STEVE INSKEEP, HOST:
Now, as you drive to work this morning, or wait for the school bus with your kids, you're going to notice that it's brighter than it was just last week. We've moved an hour of daylight from the evening to the morning with the end of Daylight Savings Time. There's new research now that this has a big downside. NPR's social science correspondent Shankar Vedantam is the man who informs us of many unseen downsides. He shares interesting ideas in social science research. Hi, Shankar.
SHANKAR VEDANTAM, BYLINE: Good morning, Steve.
INSKEEP: OK. What's the downside?
VEDANTAM: The downside appears to be a big increase in crime, Steve. I spoke with Jennifer Doleac. She's an economist at the University of Virginia. And along with Nicholas Sanders, they analyzed crime patterns in the spring and fall. And she finds that in the fall, there's a substantial increase in street crime after the end of Daylight Savings Time, especially when it comes to robbery.
I asked Doleac if she could quantify this increase, and here's what she told me.
JENNIFER DOLEAC: Our results suggest that robbery rates will actually increase by 7 percent overall. And this effect will be driven by about a 27 percent increase in robbery during the sunset hour that is affected. So, now that it's going to be dark during an early evening hour that was light before, there will be a lot more violent street crime like robbery.
VEDANTAM: Now, interestingly, Steve, Doleac did not find an increase in crimes that are typically committed indoors. So, she says, look, it's darker in the evening. It's harder to identify a robber. There are fewer eyewitnesses. So if you're a criminal, that's precisely when you actually want to take advantage of the situation.
INSKEEP: Still, I would wonder, though, Shankar Vedantam, if it's possible there are other factors like that it's, you know, seasonal. It's the holiday season. Something else is going on that would cause people to be going after others in a different way.
VEDANTAM: Yeah. So it could be that crime actually just routinely rises in the fall and falls in the spring, and that could be what's explaining it. So Doleac and Sanders took advantage of a natural experiment. Congress had extended Daylight Savings Time by four weeks in the years 2007 and 2008. So what the researchers did was they compared the crime rates in neighborhoods nationwide in those years to the crime rates in those same neighborhoods in the years 2005 and 2006.
INSKEEP: Had a chance to look at the same part of the season, but with different factors having to do with Daylight Savings or not. All right.
VEDANTAM: Exactly. And they found that when it was darker for a longer time in the evenings, there was an increase in street crimes that are committed at the hands of strangers.
INSKEEP: Just because it's darker as people go through their evening routines. That's pretty startling, Shankar. But let me ask about the other end of that. Because when it's darker in the evenings in the winter because of the way we change the time, it is lighter in the mornings, when people are also out and about and going to work. Wouldn't there be a decrease in crime on that end of things?
VEDANTAM: Well, so this would suggest that crime sort of functions like a balloon, where you press it in on one end and it pops out on the other end.
VEDANTAM: But it turns out that crime is actually much better explained by a circadian theory, which is crime is not created equally or evenly during the course of the whole day. It's disproportionately likely at certain times of the day. Here's Doleac again.
DOLEAC: Criminals just don't commit crime in the morning. Maybe they're just not early risers, or something like that. And so shifting an hour of daylight to the evening has a really big payoff in terms of reducing crime.
INSKEEP: It takes a while for a criminal to get going in the early part of the day.
VEDANTAM: You know, you have to have your breakfast, and then get ready for the day.
INSKEEP: And so we're saying that in times when there is less evening darkness to work with, a criminal would actually work less. Does that mean that policymakers should actually think about changing the way they regulate Daylight Savings Time and regular time?
VEDANTAM: You know, it could be, but it's a complicated issue, because there are lots of other factors in place. So, if you actually had more darkness in the morning, you're sending kids off to school in the dark, you could potentially be increasing traffic accidents in the morning. There are questions related to energy and what's the most efficient use of energy during the day.
So I don't think Doleac and Sanders' study necessarily tells us definitively that Daylight Savings Time is good or bad. I think it adds a data point for policymakers. I think the one thing it unambiguously does tell us is that having street lights on in the evening is probably a very, very good idea.
INSKEEP: Shankar, I hope you get home before dark.
VEDANTAM: I will try, Steve.
INSKEEP: That's NPR's science correspondent Shankar Vedantam. Of course, you can follow him on Twitter at @hiddenbrain. You can follow this program at @morningedition, @nprgreene, @nprinskeep.
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