> In 2007, Congress increased the period of daylight saving time (DST henceforth) by four weeks, adding three weeks in the spring and one in the fall. "This pro

> In 2007, Congress increased the period of daylight saving time (DST henceforth) by four weeks, adding three weeks in the spring and one in the fall. "This produced a useful natural experiment for our paper," My knee-jerk reaction to reading this is that their paper's conclusions must be based on a single observation.