…they randomly determined when officers would take the training… so it’s a really nice natural experiment. And they found that this one-day training program pretty dramatically reduced both complaints and use of force.
The killing of George Floyd has prompted a great deal of debate over whether the US should shrink its police departments. The research literature suggests that the presence of police officers does reduce crime, though they’re not cheap, and as is increasingly recognised, impose substantial harms on the populations they are meant to be protecting, especially communities of colour.
So maybe we ought to shift our focus to unconventional but effective approaches to crime prevention — approaches that would shrink the need for police or prisons and the human toll they bring with them.
Today’s guest, Jennifer Doleac — Associate Professor of Economics at Texas A&M University, and Director of the Justice Tech Lab — is an expert on empirical research into policing, law and incarceration. In this extensive interview, she highlights three alternative ways to effectively prevent crime: better street lighting, cognitive behavioral therapy, and lead abatement.
One of Jennifer’s papers used the switch into and out of daylight saving time as a ‘natural experiment’ to measure the effect of light levels on crime. One day the sun sets at 5pm; the next day it sets at 6pm. When that evening hour is dark instead of light, robberies during it roughly double.
The idea here is that if you try to rob someone in broad daylight, they might see you coming, and witnesses might later be able to identify you. You’re just more likely to get caught.
You might think: “Well, people will just commit crime in the morning instead”. But it looks like criminals aren’t early risers, and that doesn’t happen.
(Incidentally, a different experiment used the discontinuity in daylight savings time to quantify racial bias in police traffic stops.)
While we can’t keep the sun out all day, just installing more streetlights might be one of the easiest ways to cut crime, without having to hassle or punish anyone.
On her unusually rigorous podcast Probable Causation, Jennifer interviewed Aaron Chalfin, who studied what happened when very bright streetlights were randomly added to some public housing complexes but not others. His team found the lights reduced outside night-time crime by a massive 36%, even after taking account of possible displacement to other locations.
The second approach is cognitive behavioral therapy (CBT), in which you’re taught to slow down your decision-making and think through your assumptions before acting.
One randomised controlled trial looked at schools and juvenile detention facilities in Chicago, and compared kids randomly assigned to receive CBT with those who weren’t. They found the CBT course reduced rearrest rates by a third, and lowered the likelihood of a child returning to a juvenile detention facility by 20%.
Jennifer says the program isn’t that expensive, and its benefits are massive. Everyone would probably benefit from being able to talk through their problems and figure out why they make the decisions they do, but it might be especially helpful for people who’ve grown up with the trauma of violence in their lives.
A somewhat similar study of one-day ‘procedural justice’ training sessions for police officers in Chicago found they reduced civilian complaints against police by 10%.
Finally, Jennifer thinks that reducing lead levels might be the best buy of all in crime prevention.
There is really compelling evidence that lead not only increases crime, but also dramatically reduces educational outcomes.
In the US and other countries, there’s been a lengthy and mysterious drop in crime rates since the mid nineties, resulting in crime rates that are now just 25-50% of what they were in 1993.
That drop coincided with gasoline being deleaded. Before that, exhaust from cars would spread lead all over the place. While there’s no conclusive evidence that this huge drop in crime was due to kids growing up in a less polluted environment, there is compelling evidence that lead exposure does increase crime.
While average lead levels are much lower nowadays, some places still have shockingly high levels. Famously, Flint, Michigan still has major problems with lead in its water, but it’s far from the worst.
Jennifer believes that lead affects people’s brains in such a negative way that driving exposure down even further would be extremely cost-effective for its crime-reduction benefits alone, even setting aside broader benefits to people’s health.
In today’s conversation, Rob and Jennifer also cover, among many other things:
- Misconduct, hiring practices and accountability among US police
- Procedural justice training
- Overrated policy ideas
- Policies to try to reduce racial discrimination
- The effects of DNA databases
- Diversity in economics
- The quality of social science research
Get this episode by subscribing to our podcast on the world’s most pressing problems and how to solve them: type 80,000 Hours into your podcasting app. Or read the transcript below.
Producer: Keiran Harris.
Audio mastering: Ben Cordell.
Transcriptions: Zakee Ulhaq.