Jennifer Doleac and William Sanders are behavioural economists who grabbed one of those unique opportunities that occasionally crops up social science research. After all, it's impossible to really understand the effects of the social world on populations when you can't isolate the social thing you want to test for and seeing the effects.

So they - along with criminologists, lawyers, sociologists, social psychologists - had struggled for decades to identify the effect of day light on criminal activity. Until 2007.

That year, the US decided to change Daylight Savings Time.

From their study:

We exploit Daylight Saving Time (DST) as an exogenous shock to daylight, using both the discontinuous nature of the policy and the 2007 extension of DST, to consider how light impacts criminal activity. Regression discontinuity estimates show a 7% decrease in robberies following the shift to DST. As expected, effects are largest during the hours directly affected by the shift in daylight. We discuss our findings within the context of criminal decision-making and labor supply, and estimate that the 2007 DST extension resulted in $59 million in annual social cost savings from avoided robberies.

The result? Listen to the podcast for more... Or! read Under the Cover of Darkness: How Ambient Light Influences Criminal Activity here.