Daylight-saving time is a major inconvenience for criminals

Daylight-saving time is inconvenient.

Having to wake up an hour earlier on some arbitrary, often-dreary day in March is, simply put, not ideal.

Not the mention the whole making-sure-your-clocks-are-synced-up thing.

But some good does come out of the dreaded time-switch: robbery rates drop significantly.

In a recently published paper, Jennifer L. Doleac and Nicholas J. Sanders present empirical estimates of the effect of ambient light on violent crime. They found that way less robberies are committed when daylight-saving time begins in the spring, with a particularly significant drop during that extra hour of sunlight in the time right after work.

"Results show that daily cases of robbery, a violent and socially costly street crime, decrease by approximately 7% in the weeks after DST begins, with a 19% drop in the probability of any robbery occurring. A 27% decrease in the robbery rate during the sunset hours drives much of this result," they write in the paper.

Doleac and Sanders hammer out several factors why this might be the case, highlighting the fact that the "prime time for crime" is during the hours that people are on their way home from work:

1. More daylight during the 5-6 p.m. time when people are going home could discourage offenders from doing anything as there is a higher chance that they will be recognized.
2. If it's lighter outside, then there might be more people walking around outside - which would mean more witnesses. (Although, Doleac and Sanders note that, on the flip side, this could also increase the number of potential victims.)
3. The offenders' schedules might shift due to the time shift, "leaving them unavailable to commit crime until after most potential victims have gone home."

"The first two explanations imply DST has a deterrent effect on crime, while the third explanation implies an incapacitation effect that does not rely on incarceration," they note. "Regardless of the mechanism, it is clear the relationship between daylight and clock time matters when it comes to crime."

Notably, the authors add that DST does not have as great of an affect on aggravated assault, although they found "suggestive evidence of impacts for rape and murder, though results are more sensitive to time-of-year controls than robbery."

Interestingly, Doleac and Sanders also explore whether the benefits of less crime outweigh the cost increases associated with DST such as possible increased energy consumption, costly flight schedule changes for airlines, breaking up sleep patterns with the time switch, the negative effects of early school starts for middle and high school students, and, as the PTA suggested once, the risk of children "being kidnapped while waiting in the dark for a school bus."

"Most of these costs are due to the switch from standard time to DST rather than the impact of a later sunset per se, and are likely small in comparison to the benefits of the substantial drop in violent crime," argue Doleac and Sanders.

Moreover, the authors also factor in the economic angle of lower crime rates, which really gives a sense of how big of a difference this makes:

There remains the specific valuation of the social benefits of the decreased crime seen as a result of DST. McCollister et al. (2010) estimate the social cost of a robbery at $42,310. A back-of-the-envelope calculation implies the three-week extension of DST avoids $59.2 million nationally each year in avoided robberies. If we include the suggested impacts on rape (with an estimated social costs per crime of $240,776), the total social cost savings come to $246 million. These savings are from the three-week period of DST extension. General equilibrium effect are likely to vary substantially across different seasons and geographic regions, so one should do out-of-sample prediction with caution, but assuming a linear effects in other months, the implied social savings from a permanent, year-long change in ambient light would be almost twenty times higher.

In sum, yes, there are plenty of negative things to say about daylight-saving time. But there are also some serious public safety benefits.

Check out the full study and paper by Doleac and Sanders at mitpressjournals.org.