This episode features Rick Nevin, an economist who is known for his research suggesting that lead is one of the main causes of crime.
United States


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00:00:47I'm here with today's guest economist Rick Nevin Rick is a senior economist at CF International Ah he's done research on a bunch of things But maybe what he's most well known for is his research on the effects of lead exposure at a young age He's written a lot
00:01:02of papers on the topic including Are in addition to a book titled Lucifer Curves The Legacy of Lead Poisoning That is what we're going to talk about today Rick Welcome to rationally speaking Thank you So first off what Rick is thie phenomenon that the lead hypothesis was developed
00:01:20to explain You know what's the pattern in need of an explanation Well there are several patterns but probably one of people are most interested in is crime We experienced a long seemingly relentless crime increase from the early nineteen sixties through the early nineteen nineties in the US and
00:01:40then we've seen a precipitous decline since then and it is well known that early childhood lead exposure effects brain development and lowers I Q but also affect the brain in many other ways that affect impulsivity and behavior And what I found started working on this in round nineteen
00:02:04ninety four is that if you look at the rise and fall of crime and map it against the rise and fall of lead exposure with a twenty three year time lag it was an unbelievably close that and that might sound like the coincidence But we have I've since
00:02:25discovered exactly the same pattern in almost a dozen other nations around the world in that international comparison is especially striking because the crime rate started rising much faster and earlier in the US where the lead emissions started rising faster and earlier of the U S Phased out let
00:02:48in gasoline over the nineteen seventies and experienced a dramatic crime decline over the nineteen nineties Britain didn't start getting let out of gasoline until really the late nineteen eighties and they experienced a soaring violent crime rate over the nineteen nineties So it follows the same pattern in every
00:03:08country And there have been a number of other studies by other researchers at the state level the city level even at the zip code and and suburb level all of which shows a striking association between variations in early childhood lead exposure and crime rates about two decades later
00:03:28Ah and when we talk about lead exposure are we talking on Lee or primarily about leaded gasoline Or are we talking about lead paint our You know other other uses of lead Well whole lot exposure is additive by far The two most pervasive sources of exposure in the
00:03:47twentieth century were led in paint and let in gasoline And one of the striking things in my first study that that showed the the effect from either source is that we have murder rate data going back two nineteen hundred for from official mortality statistics And what I found
00:04:10was that the murder rate increased almost tenfold from nineteen hundred up through about nineteen thirty and then came down to an abnormal O in the nineteen fifties before it took off again and got back close to the peak It was that in nineteen thirty on when you when
00:04:28you map the rise and fall of lead paint and the rise and fall of leading gasoline you see that it is tracked both of those trends with about a two decade It was actually twenty one years over more than one hundred year time period Um and a lot
00:04:46of people when they think about letting gasoline are thinking only about inhalation But in fact by far the biggest source of exposure for their young children is lead contamination in household dust The brain is in a critical stage of development at exactly the age when children are beginning
00:05:08to crawl on the floor and engaging in hand to mouth activity and the deteriorated lead paint in the house settles has led in dust and the lead in gasoline emissions would settle as lead in dust And that was the primary way A number of studies have shown us
00:05:29that lead indulgence is the key pathway for the exposure of their young children They've gotten your hands in their mouth They were wet than they're crawling picked up the dust put in the hands back in their mouth and just dozing themselves with this toxic chemicals So there's a
00:05:46few links in this causal chain right There's increase or decrease in let's just say increase in lead and the surrounding environment then causes increase in inhalation Our exposure to lead some kind of consumption of led by children that causes changes in their developing brain and that causes rises
00:06:08in violent behavior So we've talked about Correlation eleven ce you know connecting that first note in the chain to the last note in the chain Do we have any any evidence for the link going from increase in lead in the environment to brain changes like Do we have
00:06:26any evidence showing that you know before we get to the actual crime rights which is in effect we think of the brain changes We've been any evidence for brain changes in children exposed to more lead than other children Yes the University of Cincinnati has done memory studies that
00:06:44showed striking evidence that children with higher levels of lead exposure have reduced gray matter in the prefrontal cortex which is the area that really effects what what they call executive functions Behavior planning and impulse control They also found that early lead exposure in pairs and reduces the development
00:07:12of Meilin which is a substance that that is deposited on the the neural connections between the connections between synapses I've heard it described as it's like insulation on a wire and as the brain grows white matter increases And that's really the Meilin being deposited on the connections between
00:07:39neurons and a number of researchers have documented that growth as we age and associate it with maur Impulsive behavior among you know teenagers and even young adults because the brain isn't fully wired is connected as completely as it is as you get older because that Meilin growth continues
00:08:03through the age of of fifty But there is particularly important in the late teens and early twenties So the impacts that have been demonstrated for lead exposure on brain growth are actually very consistent with what we already know from crime rate data about the peak ages of offending
00:08:25being in the teenage years and in their early twenties And the other thing that is particularly striking over the last twenty or thirty years that I've documented it is that we've seen a shift in that peak age of offending The most dramatic declines that we have seen in
00:08:43arrest rates by age have been among juveniles and then substantially among people in their twenties and thirties And although the overall crime rate is coming down it actually would be coming down even faster except that we're still seen an increase in arrest rates for older adults in absolute
00:09:08terms people in their forties and fifties they're still less likely to be arrested than people in their team's early twenties But in temporal terms people in their forties and fifties today are more likely to get arrested than they were thirty years ago whereas there's been an eighty or
00:09:28or even ninety percent decline in some crime categories for juvenile arrest rates So what you're saying is that arrest rates are still being affected even among the whole the stage groups by the years before the phaseout of letting gasoline because that's when those groups were born So I
00:09:53I don't yet understand how that how that connects to the thing I'm about to say But but I reading about the lead and crime hypothesis and potential objections to it One of the main things that came up was thie claim that in the nineteen nineties the crime rate
00:10:11you know in the latter half the decade and onward the crime rate went down But it didn't just go down Among people who were born in nineteen seventy mid early mid seventies or later it went down among a bunch of different age groups Ah which seems like evidence
00:10:26against the hypothesis that it's like a cohort problem that it's like a group of people who are more likely to commit crimes as opposed to some ah period issue Where like there's something about you know cities in that era that makes people more or less likely to commit
00:10:40crimes like you know a crack epidemic or something like that Yes there is that there was a study that brought up that point in two thousand two and and it was it was a good it was a good question to ask It was a good study in many
00:10:54ways but they actually focused rather narrowly on homicide and and then they focus I actually on homicide victimization rates by age And so as opposed to committing homicide yes and well there There is no data that is perfect And of course the problem with when you're looking at
00:11:17arrest rates they might go up from one year to the next even if the overall crime rate is going down because the police might catch more of the people who committed crimes so they focused more on the victimization rate by age And and they noted that there was
00:11:38a very strong correlation historically between arrest rates and homicide victimization rates by age that that correlation mean that people commit homicides are likely The age of the perpetrator is correlate with the age of the victim Is that what you're saying Correct Correct And of course the most obvious
00:11:56example is street gangs I mean then that that was the problem the biggest source of concern particularly eighties on the nineties But but one of the things I point out in Lucifer curves is that the that correlation has weakened and the percentage of juveniles who are murdered by
00:12:18other juveniles has dropped substantially And those who are still being homicide victims are more likely to be victims of adult homicide offender's But more importantly looking at at other broader category of arrest rates over a longer period of time I've found incredibly consistent relationship because the crime decline
00:12:44has now spread around the world with most countries having phased outlet in gasoline during the nineteen eighties And if you look at a rust rates by age not only is it very clear that we've seen a much steeper decline in youth You know in juvenile arrests in the
00:13:02United States you're seen exactly the same pattern in Canada in Britain in Australia in New Zealand So it's It's a very clear pattern that has become a parent since those studies questioned that cohort effect Another point on that subject is that and we haven't sometimes heated debate over
00:13:27incarceration in the United States is going on now and it's been a little frustrating for me that people have not noticed the same cohort effect in the prison population The overall US prison population has been declining for the last two years but people feel like you know it
00:13:47should be much lower than it is What you know What kind of sentencing reforms can we enact And some of those might be very good changes to make But we should be aware of the fact that we've seen absolutely stunning declines of seventy percent arm or in the
00:14:05male incarceration rate for cretin in nineteen year olds We've seen declines of more than fifty percent in the incarceration rates for men in their twenties and the overall And once again the overall incarceration rate is not declining as fast Because the incarceration rates are increasing for people over
00:14:26the age of forty five or fifty why would they be increasing Like I presume the delight hypothesis doesn't seem like it would predict that Well what What is happening unfortunately is that resistive is um rates among released prisoners are quite high particularly among state prisoners And what is
00:14:52happening is that the percentage of people over the age of fifty that are in prison is increasing in no small part because they have been to prison once or twice or Mohr during the course of their lives and have racked up another serious offense and have gone back
00:15:12to prison as they've gotten older just in here again Here again In absolute terms the incarceration rate for people over the age of fifty is lower than it is for men in their thirties But in relative terms over time the incarceration rate is actually increasing over the last
00:15:33twenty thirty years for people over the age of fifty as it has been plummeting for juvenile's and young adults Were there any predictions that you are or that thiss theory made when it was first being formulated in the late nineties early to thousands that were born out by
00:15:55the data since then So you know in fifteen twenty years yes In the first study I was anticipating continuing declines in the crime rate because you're looking at ah roughly a two decade lag twenty three years for violent crime and I found it was close to eighteen years
00:16:14for property crime which is actually another source of evidence Because property crimes are much more likely be committed by teenagers then violent crime is is But the The implicit forecast was that there would be considerable ongoing declines in crime rates and especially in arrest rates for younger adults
00:16:39and that has been borne out in the United States My two thousand seven study that looked at seven or eight different countries around the world had the same implicit forecast And in Lucifer curves I actually show the crime trend up through the last year of mine Peer reviewed
00:17:01published analysis and then show this stunning in many cases fifty percent decliner or more in burglary and robbery rates in half a dozen different countries that have tracked what the earlier decline in lead exposure suggested What happened So it's had better predictive value than any other criminal justice
00:17:25theory I'm aware of Is it surprising though conditional on the lead hypothesis being being correct and explaining Ah you know majority or large plurality of the variants and crime Is it surprising that crime continues to go down You know in the twenty tens if the lead you know
00:17:45let was phased out decades ago Well well we've We've always had a distribution of blood lead levels and there's no lower threshold that any research has suggested below this level there's no impact And as blood lead levels continue to decline with ongoing progress in reducing lead paint hazards
00:18:14and other sources of light exposure I'm keeping an eye on the percentage of children that still have a blood that level above five At least one study that was their carefully done I think there was also by the University of Cincinnati found that there was an elevated risk
00:18:33of criminal behavior at least above a level of five will in the nineteen seventies Five was an incredibly low blood lead levels So like a lot of other public health risk There is almost certainly an interaction between the environmental exposure and individual variations in biological vulnerability that we
00:18:57we might not fully understand And what that might mean is that among a group of young children with blood of bubbles above thirty you might have an incredibly horrific young making numbers up But just for illustration it might be fifty percent of those children end up in the
00:19:16criminal justice system If you look at children with blood lead levels of ten to twenty it might be ten percent of them end up in the criminal justice system It could be that you know you're still getting four five percent of children with blood levels of five to
00:19:34ten that end up in the criminal justice system and we'll find out how much farther this goes because we have seen on encouraging ongoing substantial decline the percentage of children with blood of levels above five and fascinating thing that is not in my book But part of my
00:19:55ongoing work is that the juvenile restaurants are continuing to decline tracking that earlier decline in the percentage of children above five And if it continues on this relatively consistent trend that it's being on of the last twenty five years juvenile rust rates could be remarkably close to zero
00:20:16Sometime around twenty twenty five it was a oh so you're saying that levels of lead have in fact been going down So it's not surprising conditional on the lead hypothesis that we see crime guys still go Yes we're definitely the level of concern that the CDC has now
00:20:34set and they're likely to lower it in the near future But they've said anyone above five and I should pause here because as muchas as a public health policy it's extremely important From my perspective I think we want all children under too not just under five The level
00:20:56they tracked over the years has declined In the nineteen sixties Child was not called blood poison Unless that a blood lead level above sixty Well let it drop that it was horrible Then it dropped to forty when they had large scales bringing programmes in several major cities In
00:21:15the early nineteen seventies almost a third of the children tested were above forty Then it dropped twenty thirty and then two twenty five and then ten and now it's at five and like that go lower As all the evidence continues to show There's no lower threshold where there's
00:21:34no impact at all But I am a little bit concerned when you hear agreed news stories and several other prominent researchers have noted the same thing in published reports that if you're in a situation like we've had in Flint where children are described as lead poisoned and are
00:21:52being given the impression that they are irreparably damaged because they had a blood lead level above five well the first national survey of children's blood lead levels in the late nineteen seventies found that ninety nine point eight percent of all children have blood lead levels Oh five huh
00:22:13So I don't want anyone I don't want any child have a blood level above five I don't even want anyone to have a blood lead level above too But I don't want to scare the living hell out of parents or children who have one blood test of six
00:22:29or seven because a lot of people have done just fine after having that experience Now that that is a really good point I'm actually surprised given that I get what you're you said this was but the time when a large proportion of children were tested above forty I'm
00:22:46surprised that crime wasn't even higher than than it actually was If that was the level lead exposure Well yeah and that was in cities in the air Lead levels in cities were much worse than they were in suburbs and this is another part of peace Of the evidence
00:23:03that supports this theory the murder rate declined since the nineteen nineties has been especially steep in the largest cities and we have the air lead data from twenty years earlier Sure on that The greater traffic congestion in those cities naturally led to much higher ambient air lead levels
00:23:25in large cities than you ever saw in suburbs So you have the concentration of crime that has been in cities as opposed to suburbs and rural areas in decades past was also consistent with the much higher erlynne levels that had been recorded in cities twenty years earlier And
00:23:46we've seen the decline go down much more steeply in those areas where the air lead levels have come down the most stately This also has had a very important racial impacts because black children were disproportionately concentrated first in dilapidated city slum housing that had horrible lead paint breasts
00:24:11and then in cities in general where the air above levels were higher and then in particular in public housing projects that we unfortunately built in many cases right beside new highways where the near fallout from the street was much worse than the overall ambient air lead levels And
00:24:31this led to especially high arrest rates among black juveniles in the eighties and early nineteen nineties And did we see those especially elevated arrest rates near the highways Or just are we talking about in general among black people Well you don't have You don't have any systematic data
00:24:52But in my two thousand seven study I specifically noted a notorious housing project on the South side of Chicago that was eventually tourney down and it had been built right beside I think it's the Dan Ryan Expressway that is one point is sixteen lanes wide and I just
00:25:14I described what we know about how much more severe the near fallout is and by the time they started emptying out that project and just decided to tear it down It was accounting for I forget with percentage was but it was a shocking least substantial percentage of all
00:25:31of the murders in Chicago were occurring in that housing project So there's anecdotal evidence that is very consistent with near road exposure being especially severe and affecting not just the children you know Children are especially affected by let in dust at their main pathway but they're also affected
00:25:54before birth and through the mother's blood of level And pregnant women in those housing projects were breathing Ah horrific amount of light in and out all right all the time that they were pregnant So all of the anecdotal evidence continues Tow line up with that Yeah And as
00:26:12an aside people are generally unaware of the fact that black felony by juvenile felony arrest rates now are less than one half of what the white juvenile felony arrest rates were in the early nineteen eighties and you can see the much steeper decline in black juvenile arrest rates
00:26:36over the last twenty thirty years That is again completely consistent with the much steeper decline in more severely elevated blood lead levels among black children twenty years earlier that so The idea is that exposure to lead was greater among young black people on among young white people And
00:26:54therefore reducing lead in the environment produced a sharper decline in crime among young black people Then white people Exactly Yeah okay And that that that disparity that racial disparity in lead exposure and especially in sports severely elevated But the levels has been very well documented since the nineteen
00:27:15seventies So we know that happened So at the beginning toward the beginning of this conversation I was asking about the link in the causal chain between exposure to lead and changes in the brain On DH you talked about some of the like neurological evidence we have for for
00:27:33brain changes But do we have any Any other evidence in the population of behavior Like if the reason that led increases crime is because it makes people you know more impulsive give gives them lower impulse control etcetera Do we have any evidence of of trends that would also
00:27:56result from low impulse control etcetera Like I don't know people going into more debt or something like making worse financial choices That thing there are two actually mean the phaseout of of letting gasoline was Actually the cost was justified by the anticipated benefit of that our educational achievement
00:28:19and higher lifetime earnings as a result of them in some researcher named Joel Schwartz who actually won the MacArthur Award I believe for his work on this subject put together this perspective that there was a strong association between Q levels and education attainment and subsequent lifetime earnings and
00:28:42there's a lot of research you and as early as the nineteen sixties or especially in the seventies that showed that lead clearly had an impact on I Q scores and putting those two together he said If we if we reduce childhood love exposure you're going to increase education
00:29:01attainment and significantly increased lifetime earnings As a result well the other one of the things I've looked at it it's not as he's at a map We're analyze statistically But the trends are pretty clear that we had significant increases in high school graduation rates up through the nineteen
00:29:23fifties At sometime in the nineteen sixties about twenty years after the air lead levels took off after World War two the progress in educational attainment mostly stalled for almost twenty or thirty years in some cases went down What we've seen going on in education trends over the same
00:29:46years of the juvenile and young adult of rust rates have plummeted is that the high school dropout rate has fallen to an all time record low and college men enrollment rates have risen to an all time record high so that by itself doesn't prove the association But it's
00:30:06exactly what we would expect to see But the other relationship the other relationship that is really stunning and people have a hard time wrapping their head around is that in my two thousand study some research head a number of studies had already shown a length between like and
00:30:28criminal behavior and incarceration risk But another study had shown that there was also a clear length with unwed birth rates At the same time that the crime rate rose The young white birth rates and particularly teenage on wed birthrates really went up from the sixties all the way
00:30:49through the early nineteen nineties and my study in two thousand tracked I looked at both unwed birth rates and abortion rates and found that it was exactly the same pattern as crime and that it had risen And in fact the time lag fit with which with the age
00:31:11group you were looking at that the young The birth rate for girls under the age of fifteen seemed to map at a fourteen year lag for girls fifteen to seventeen of map that a seventeen year leg for eighteen and nineteen It mapped out a twenty year leg and
00:31:29we've seen a massive stunning decline in in teenage birth rates in general unwed birth rates in particular end and in abortion raids And it's the same pattern if you look across age groups that you see in the crime and incarceration rates that the over forty is the only
00:31:53group where unwed birthrates or abortion rates are still increasing even slightly that you've seen the massive steep decline in the younger age groups and I'm currently working I've got the data but I haven't published anything on a study that shows exactly the same association The same trends in
00:32:14unwed birth an abortion rates in Britain and in Canada late to there their lead exposure trends There's one thing I wanted to ask you about in your book You talk about how people back in the eighteen hundreds were already worried about the effects of lead exposure Um I
00:32:31guess it was higher lead exposure than then Just you know inhaling lead dust near a highway There are like kids working in lead mines But so who's wondering first Can you give an example of ah of concerns raised you know back in the nineteenth century about lead But
00:32:50then second if we knew back then that lead has had these negative effects on people's brains why did we suddenly start using it widely in the mid twentieth century Well there isn't a good answer to that question It was a horrible mistake obviously And it's it's ah cautionary
00:33:14tale Because people today think Well you know I said ninety nine point eight percent of children had blood that levels above five in the late seventy So how can you be at all worried about any percentage of kids being above five Well it can still be affecting some
00:33:30part of the population and in the eighteen hundreds what happened is that they actually would refer to the lead trades and lead poisoning in the encyclopedia was called a disease of occupations and they were especially aware of effects One painters and type setters had horrible exposure and there
00:33:53were other professions in the early decades of the Industrial Revolution where lead exposure was widely recognized as a serious occupational hazard for a variety of workers And we were talking about people dying We weren't talking about losing a few points There was no understanding at that time of
00:34:19how this might be affecting very young children and they would be affected both by industrial emissions There was increasing concern about the paint lead levels and France actually started reducing their paint Lead levels in the mid eighteen hundreds are actually around eighteen forty and I've I've found crime
00:34:44data from the eighteen hundreds that showed a steep decline in French crime over the eighteen hundreds and a similar shift in arrest rates by age in Britain to what we're seeing now The term juvenile delinquency actually was first used in the early eighteen hundreds at the dawn of
00:35:08the Industrial Revolution about ten to twenty years after there had been explosive growth in the number of patents for lead paint and the production of lead to be used in lead paint And then over the eighteen hundreds Britain caught up with France phasing out the lead in paint
00:35:28and they they saw not only a significant decline in British crime or related to hundreds They also saw a shift from juvenile delinquents too much older offenders that's just recently been documented in a study exciting Lucifer turns So you're seeing this pattern in hindsight going back all the
00:35:50way to eighteen hundred But when they first added led to Gas Lane there were people prominent public health advocates who were trying to block this They had been working to reduce leaden paint and trying to make people more aware of the hazards toe workers from lead poisoning And
00:36:13there were people who when they were discussing this possibility We're saying If this gets to a point where there are a lot of cars and this is being spewed everywhere it just seems like you could have some very profound pervasive effects man And of course those warnings turned
00:36:32out to be right and to give you an idea of how little regard they had for the warnings that they were facing at that time the Tetra Ethyl lead manufacturer When they first started producing this to reduce engine knock in in with the gasoline lead additive they had
00:36:56They called it loony gas at the plant where it was made A number of workers died and so a lot of others were taken away in straitjackets God and it was pulled off of the market Led additives were pulled off the market for gasoline for I think it
00:37:13was a year or two And then there was you know corporate pressure and the attorney the the federal government was involved and they announced Okay well it was just They didn't have the proper ventilation The plan It's not going to be a problem in the gas lane And
00:37:31leaded gasoline was back And then that was the beginning of the long rise in air lead levels Are there any specific villains that we can You know I want someone to be mad at is there like a person who made this decision There are a lot of good
00:37:46candidates that I'm I know that there have been other books that are written on that subject but I haven't really focused on that so I'd rather not call them on game The fight thing is that one of the one of the leading scientists working for the oil companies
00:38:06and Ock tell them in the manufacture of the of the lead additive he was They tried to get him involved in a defense of Lead Paint Cos And he refused to help them defend that case because he said that he had seen evidence of children in the nineteen
00:38:31forties with when they first recognize the link between leg poisoning from paint chip ingestion and other sources of lead ingestion and children and the risk of what is now called intellectual disability Um that was discovered in the early nineteen forties and the same scientist who was saying Yes
00:38:52I've seen this affect myself It's a serious risk I can't defend the paint companies I think he was the same scientist urging the use of letting gasoline so people can be blind I hope I have that story correct that she should have emphasized again before I got into
00:39:07it that this is not where I focus my research I've I'd rather stick to the game and just get rid of the exposures we still have There are a lot of other people out there who have sued the paint companies and I wished them well But that's not
00:39:21where I can probably do the most understanding How has THIE reception to the lead I pops this bin and and also what do you think it would take to get sort of mainstream consensus on board and taking action in response For many years people was just largely ignored
00:39:40And there was no I got very good article in the of Baltimore newspaper When my two thousand study was published I thought sure it would generate another Collins whom Or interesting and it never did The Washington Post did a great article after my two thousand seven study was
00:39:59published They actually the acts We had a front page article in the post two years later about how crime was continuing to decline and no one could explain why And you're over there waving Hello Hey hey I actually I called the reporter who wrote the story on my
00:40:19research two years earlier and said If you'd seen this he said Yeah I talked to them before they published I sent my earlier study They just decided to be Oh I've had more luck in the last few years thanks to Kevin and draw us who did a cover
00:40:35story And Kevin not only wrote the cover story on this but as a daily blogger he's continued to follow up on us and and directed people to all of the different research But he's also posted a blawg post on how they had tried to interest the New York
00:40:54Times of the LATimes or other newspapers into you know showing this relationship that he would do a shortened version of the article you did for Mother Jones or update things And for some reason they're not interested It's just rather frustrating and it relates as I say not only
00:41:14to the lead hypothesis but two clear effects of this that you would think people would be acknowledging if we're having the debate we're having today about mass incarceration someone should be paying to attention the fact that we're already seeing a seventy percent decline in the eighteen and nineteen
00:41:35year old incarceration rate and that that is going to roll through the prison system Overtime I mean even simple capital expenditure decisions I forgot it was Alabama or Mississippi last year Last couple years have been debating a massive spending program to replace aging prisons and it would be
00:41:59financed over a thirty year period of time with thirty year bonds And no one has looked at what's happening by age group in prisons to know that they were There's no way they're going to need that much present capacity in thirty years I wonder If so you would
00:42:16think at least those facts would be concerned Justice from the self interested financial perspective Ah so I wonder if it would be helpful to make some concrete predictions over for you know the next five to ten years Say that are like you know probabilistic predictions about a bunch
00:42:35of things that like if you can demonstrate like strong predictive power of this hypothesis that like in five to ten years that might I mean especially if you could get people to agree ahead of time to like yes if those predictions come true then are like some percentage
00:42:51of those predictions come true Then like we will consider that like strong evidence for the lead hypothesis Well the funny thing is it's still the same prediction on and I can't I can't tell if there is some baseline crime rate level that would exist with zero lead exposure
00:43:10I'm starting to think that there might not be really You think the most But I mean there was crime before leg raise two zero like the truth is lead paint started spreading in Europe in the seventeen hundreds I don't think we have data on anything huh In history
00:43:30without lead exposure But there was violence at least write like mean Steven Pinker is talked about rates of violence Well before we had lead paint we might not have called a crime of back then But yeah I don't know I and or certain places in the world although
00:43:51this is getting into material I haven't published But I've actually come across a couple of historical things about well you know a period of accentuated warfare that couldn't be explained among Native Americans in the Southwest United States And for some reason there was horrifically violent warfare that didn't
00:44:14seem to compare with anything at other times or in other parts of the country And I've come across the evidence that Native American tribes in that era were they discovered lead at the Sarah Lows Mountain on DH There were incredibly high lead content levels in these ceramics that
00:44:37they ate and drank from that its interests So it's it's I keep seeing it over and over again and I don't think we've you know in an era of data And this is particularly relevant toe like because the very first I Q tests were created at the beginning
00:44:58of the twentieth century Around nineteen hundred the bene test in France was in nineteen o four and that was one of the first and most significant and dances and unite to testing And of course France had already dealt with what they had understood was a dangerous increase in
00:45:19leading paint you know starting one hundred years before that test Well now people look and they talk about how does lead exposure effect like you I'm starting to think we should be asking a more profound question What does like you even measure in the absence of any lead
00:45:38exposure I'm not sure we know And I know for certain that these studies that have shown an incredibly strong correlation between HQ you and education attainment and unwed birth rates in criminal behavior Well as you see particularly among juvenile's those rates plummeting and over twenty five years establishing
00:46:03a trend line that as I said before shows them getting close to zero in twenty twenty five The way that they calculate I Q is always relative in relative terms so some percentage of the population will always be under seventy five and some percentage will be between ninety
00:46:23and one ten etcetera But it's not going to mean what it used to me in Munich There are actually a variance in the population there Well you might You can still come up with this person has a very low score in relative terms but in in absolute life
00:46:41terms How much does that affect their potential I don't think anywhere near a CZ much as it did in the nineteen sixties or seventies when what you were really measuring was the biggest part of what you are measuring with I Q test was how much how severe was
00:47:00the early childhood lead exposure for this child Does that model fit with the ah apparent hereditary nous of like you know significant hereditary ness of like you Well one of the things I've pointed out is that there are two trends that have been well documented In eye to
00:47:18one is that this is mostly done on siblings that are separated and especially twin That's the ideal data If they're separated very early in life and then you you find that the genetic siblings that never knew each other after the age of one there are accused tend to
00:47:41be closer than either Either of them are with their adopted similar hates that grew up in the same household But when you understand the impact of lead exposure is very substantial before birth through maternal blood but and that the peak period of ingestion is when children are learning
00:48:02to crawl around the age of six months and I've looked at some of these adoption studies It's very often children who were adopted after six months at around the age of one or older Interesting So just so that people are assuming well they have nothing in common from
00:48:18their birth life Well no They crawled on the same floor and adjusted the same lead dust and shared the same maternal blood blood And furthermore they could inherit the same biological vulnerability Toe let exposure right That's shows modifiers Yeah you might have You might But that would be
00:48:38irrelevant if we eliminated lot explosion Interesting So it's an intriguing The other trend though is that a guy by the name of Flynn actually discovered comparing IQ test norms over many decades in I think more than two dozen countries around the world has shown that Hi Q scores
00:49:04have been rising substantially for more than a century everywhere in the world right The way they calculate I too obscures that rise because every new I Q test your IQ was calculated relative to the other people in the norm Sample for that I Q test But when they
00:49:24haven't no I Q test They also give people the older I Q test to prove that it's consistent that they knew I Q test is scoring people as having high I Q If they had hired you on the old test and low I Q If they had low
00:49:38I Q on the old does what Flynn discovered is that when you look at these norm comparisons as they're called the new Ike sample always are almost always scores above one hundred on the old test on average And one hundred by definition was the average for the people
00:50:00who were the norm sample for that test twenty or thirty years earlier So that means it was actually increasing And in my two thousand study I pointed out that a lot of the data that Flynn had was consistent with the steep declines in lead paint exposure that would
00:50:22have occurred in Europe starting in the middle eight eighteen hundreds and in the United States starting around nineteen hundred So I think there are really in people have never understood How do we have never really been able to explain the clinic And they've had different speculative ideas about
00:50:45like Maybe our education system is teaching analytical skills more so something like that Yeah yeah but that it That is interesting One other question that I meant to ask earlier but forgot is Do we have there been any attempts to exploit like pseudo random variation in looking at
00:51:06these correlations Like obviously we can do a really randomized controlled trial where we assigned some children to grow up lead and others not but but sometimes economists get very clever about exploiting these kind of natural experiments Well one of one of I think the most striking natural experiments
00:51:22is the fact that I mentioned earlier that the US increase in lead emissions after World War two was much greater and much earlier Then it was in Britain and other places that were struggling to recover um from the devastation of that war and had nowhere near the number
00:51:45of automobiles and nowhere near the gasoline consumption that we had in the nineteen fifties And then the fact that the phaseout of lead in gasoline occured in you know different times sometimes ten or more years apart in different countries and then you see that you've got the same
00:52:04time lag explaining the rise and fall in crime in every one of the countries that I've looked at and and predicting another dozen years of steep declines in those countries But it's the lag related to the rise and fall of lead within that country So that's that's a
00:52:24pretty striking natural experiment But no one planned on that confirms the relationship overall and the other thing is that the other thing is the change by age That I think is is the most striking Ah that we're still seeing such steep declines ongoing declines in juvenile restaurants Cool
00:52:44Well that's probably a good place to wrap up But before I let you go Rick I wanted to ask you to nominate a book or or article or website or something like that that that either had some significant influence on your thinking or that you consider to be
00:53:02like a great representative of of your field like really well conducted experiment or you know well argued or something like that What have you got Well I think this is not really about lead poisoning director Fine Yeah but the there's a book called The Rising Curve and it
00:53:21was edited by a very well respected academic by the name of Alright Nicer who passed away a few years ago and when the book The Bell Curve came out which was extremely controversial And it came out in the early nineties and talked about how I Q affected crime
00:53:43and on what births and education attainment and you know he cited they cited the research showing like was inherited over it Nicer was the person that the American Psychological Association chose to be the chair of the committee that produced a paper called Intelligence Knowns and Unknowns to try
00:54:03and deal with the extreme controversy created by the Bell Curve in the course of writing that paper if he found them The research on the Flynn effect and related trends on the narrowing of of black and white achievement score differences in school were you to really fascinating subjects
00:54:29that he wanted to look at Maur and James Flynn was the author of one of the chapters of that book He also had other distinguished academics authoring on This is of the rising terms So after the publication of The Bell Curve the Rising Curve was published got nowhere
00:54:50near as much attention as the Bell curve didn't But I think is a really interesting piece of background to provide perspective on other things that you might have heard about you and particularly haven't noted that and I've been lucky enough Both James Flynn and All Rig Nicer had
00:55:08traded e mails with me when I was first when this work around two thousand encouraging me because the mystery had not been solved and they thought I might be onto something So I would strongly recommend the rising curve as a good example of of really rigorous and principled
00:55:28academic thought including an acknowledgement of We can't really explain this yet You know in the case of James Flynn in particular Flynn had documented it gets more credit than that they actually call rising I curved trend the Flynn effect No And even though he was credited with discovering
00:55:47it he makes it clear in the rising curve that he doesn't think that any of the other explanation any of the explanations for it are satisfactory There's something else missing I'm convinced that it's lead but Well that's that Something a great recommendation in part personally because I have
00:56:11a weakness for book titles that reference earlier book titles as a response to them Like like there was a pair of books I forget to be authors but one was titled How the Mind Works Then the second one was titled The Mind Doesn't Work that Way Like a
00:56:27Girl So now we have the bell curve in the writing that is That's what you think that was the inspiration for the title of Lucifer Kurds Because really because they have a plane in the first chapter that um there's actually relationship between lead contamination in the atmosphere and
00:56:48the origin of the word Lucifer and what I'm suggesting What I'm suggesting is that both the the bell curve and the rise and fall of violent crime that I have I have both of those on the cover Those are both impacts of lead exposure and it's following on
00:57:09the bell curve and the rising curve So now you think about the word Lucifer Yeah that's perfect Tell me about the word Lucifer Where does that come from Well it's just a fast and tidbit that I picked up that I realized that could use Ben the word Lucifer
00:57:26is commonly thought to be another name for Satan or the devil but right But biblical experts say this is actually a mistake of of of ancient biblical translation that the word Lucifer refers to Venus a CZ the Morning Star and in the Latin version of the Bible that
00:57:52loose a pheromone However the Latin word was phrased was used in many references to Jesus Christ when that were then translated into the English Bible as the rising star of the morning star In references to Christ there was an Old Testament reference to a Babylonian king who likened
00:58:15himself to the Babylonian God of of Venus And it was a ridiculing commentary to call him Lucifer and for some reason when it was from the Bible is translated into English I guess the King James version that was the only place that the word Lucifer was kept And
00:58:37I pointed out that the reason that Venus is so bright in the sky the reason the Morning star is so bright we now know from space expeditions is because of its incredibly dense incredibly toxic atmosphere That reflects late and the heat on the planet is so high that
00:59:00it actually melts lead on the surface and that led settles on the mountains as a glistening reflective shield So I point pointed out as a new perspective on crime that Lucifer isn't actually the name of the devil and doesn't even represent anything inherently evil It just refers to
00:59:24the the the impact of an extremely contaminated toxic lead environment So that's that I love Cem Cem Good entomology Epidemiology Public health Well thank you so much for coming on the show This is fascinating Will link to the rising curve and the Lucifer curve A swells to a
00:59:49couple of your papers on the topic Thank you This concludes another episode of Rationally speaking Join us next time for more explorations on the borderlands between reason and nonsense

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