Making daylight saving time permanent — by never “falling back” again — could save the country billions a year in social costs by reducing rapes and robberies that take place in the evening hours, according to a forthcoming paper by researchers at the Brookings Institution and Cornell University.
In 2007, Congress increased the period of daylight saving time by four weeks, adding three weeks in the spring and one in the fall. “This produced a useful natural experiment for our paper,” authors Jennifer Doleac and Nicholas Sanders write at Brookings, “which helped us isolate the effect of daylight from other seasonal factors that might affect crime.” They found that “when DST begins in the spring, robbery rates for the entire day fall an average of 7 percent, with a much larger 27 percent drop during the evening hour that gained some extra sunlight.”
The mechanism that might cause this drop is fairly simple: “Most street crime occurs in the evening around common commuting hours of 5 to 8 p.m.,” the authors write, “and more ambient light during typical high-crime hours makes it easier for victims and passers-by to see potential threats and later identify wrongdoers.”
Moreover, according to the paper, the drop in crime during evening hours wasn’t accompanied by a rise in crime during the morning hours. Criminals aren’t morning people, as it turns out. In addition to the decrease in robbery rates, the researchers found “suggestive evidence” of a decrease in the incidence of rape during the evening hours, as well.