He refers to this graph, but not any of the research on the various other predictions that you could derive from the hypothesis that lead caused much of the hump in crime over the past 60 years.
Can you name some of these predictions? Can you link to some of the research? What exactly are you referring to?
3 predictions that I came up with, when I heard about the hypothesis:
The lead hypothesis predicts a cohort effect: the crime rate for 35-year-olds should drop 10 years after the crime rate drops for 25-year-olds. Many competing hypotheses (like new policing tactics) predict a cross-sectional effect: the crime rate for 35-year-olds drops at the same time that the crime rate drops for 25-year-olds. (Although there may be feedback effects which cause some smudging of this sharp distinction, e.g. more crime among a subgroup means that police are spread thinner which makes crime more attractive for everyone.)
The lead hypothesis makes pretty specific predictions about differences in the timing of the crime drop across different regions. If one jurisdiction removes lead 8 years after another jurisdiction, then their crime rate should drop 8 years later.
The lead hypothesis predicts differences in the size of the crime increase & drop across different regions. If one region had more environmental lead than another, then it should have both a larger increase in crime during the “increasing crime rates” time period and a larger drop in crime during the “declining crime rates” time period.
I looked at one of Nevin’s papers shortly after the Drum piece originally came out and it had some evidence for all 3 predictions, though not with as much rigor/precision/detail as I would’ve liked. For example, on prediction #3 it compared larger cities (which had more driving per unit area, and thus more environmental lead due to gasoline) to smaller cities and showed that their crime rates matched this pattern.
There is also research on other steps in the long chain (e.g., measuring blood levels of lead), and on other outcomes attributed to lead (e.g., teen pregnancy rates), some of which is mentioned in Drum’s original piece. I haven’t looked into that research beyond what I’ve seen in the popular press articles.
I think the paper that I looked at was The Answer is Lead Poisoning. Mainly just looking at the graphs & tables.
The city size pattern is not a unique prediction of the lead hypothesis (there are various other differences between large & small cities which could account for it, though nothing that strikes me as overwhelmingly obvious), but it is a relatively unambiguous prediction (especially if there’s high quality data on city size vs. environmental lead levels—I’m not sure how good those data are). If large vs. small cities turned out not to have this difference in crime trends then that would be pretty strong evidence against the lead hypothesis, so the fact that the comparison did come out this way must be at least some evidence in favor of the lead hypothesis.
Can you name some of these predictions? Can you link to some of the research? What exactly are you referring to?
3 predictions that I came up with, when I heard about the hypothesis:
The lead hypothesis predicts a cohort effect: the crime rate for 35-year-olds should drop 10 years after the crime rate drops for 25-year-olds. Many competing hypotheses (like new policing tactics) predict a cross-sectional effect: the crime rate for 35-year-olds drops at the same time that the crime rate drops for 25-year-olds. (Although there may be feedback effects which cause some smudging of this sharp distinction, e.g. more crime among a subgroup means that police are spread thinner which makes crime more attractive for everyone.)
The lead hypothesis makes pretty specific predictions about differences in the timing of the crime drop across different regions. If one jurisdiction removes lead 8 years after another jurisdiction, then their crime rate should drop 8 years later.
The lead hypothesis predicts differences in the size of the crime increase & drop across different regions. If one region had more environmental lead than another, then it should have both a larger increase in crime during the “increasing crime rates” time period and a larger drop in crime during the “declining crime rates” time period.
I looked at one of Nevin’s papers shortly after the Drum piece originally came out and it had some evidence for all 3 predictions, though not with as much rigor/precision/detail as I would’ve liked. For example, on prediction #3 it compared larger cities (which had more driving per unit area, and thus more environmental lead due to gasoline) to smaller cities and showed that their crime rates matched this pattern.
There is also research on other steps in the long chain (e.g., measuring blood levels of lead), and on other outcomes attributed to lead (e.g., teen pregnancy rates), some of which is mentioned in Drum’s original piece. I haven’t looked into that research beyond what I’ve seen in the popular press articles.
Do you think you could link to that paper?
A Larger vs. smaller cities comparison sounds like it has ample room for confounding factors, no?
The other outcomes attributed to lead sound like they correlate with crime rates, so this isn’t independent evidence for the lead hypothesis.
I think the paper that I looked at was The Answer is Lead Poisoning. Mainly just looking at the graphs & tables.
The city size pattern is not a unique prediction of the lead hypothesis (there are various other differences between large & small cities which could account for it, though nothing that strikes me as overwhelmingly obvious), but it is a relatively unambiguous prediction (especially if there’s high quality data on city size vs. environmental lead levels—I’m not sure how good those data are). If large vs. small cities turned out not to have this difference in crime trends then that would be pretty strong evidence against the lead hypothesis, so the fact that the comparison did come out this way must be at least some evidence in favor of the lead hypothesis.