Are we getting an hour more sleep after last Saturday night, or an hour less? The answer, as millions of Canadian households gloomily found out on March 10th, is that clocks across Canada moved an hour forward. As we begin the controversial phenomenon of daylight saving time, this nuisance to sleepy office workers offers a respite for the criminal justice system.
There is a growing body of research indicating that the beginning of daylight saving time in the Spring reduces the incidence of most crimes. According to research conducted by Ignacio Munyo, the 1-hour loss of sleep in the spring may reduce aggregate crime rates.1 This alteration in criminal behaviour is because crime is a response to incentives. Criminal behaviour is engaged in when the expected benefit of the behaviour exceeds the expected costs, and expected costs includes both the possibility of criminal punishment and opportunity cost. While criminal punishment does not increase after daylight saving time (barring a grumpier judge), this lack of sleep elevates the opportunity cost of crime by increasing the perceived value of sleep. Put simply, the more tired a potential offender is, the more likely they are to value sleep above committing the crime.
Additionally, Jennifer Doleac and Nicholas Sanders found that additional daylight in the evening after daylight saving time may reduce crime rates.2 Specifically, they hypothesize that as criminals primarily operate at night, more daylight in the evening increases the likelihood that criminals will be caught. This increases the opportunity cost of criminal activity, and thus disincentivizes criminal behaviour. Empirically, after the beginning of daylight saving time in the spring, robbery rates dropped 27% during the evening hour that gained additional sunlight, as well as an average of 7% the rest of the day.
Doleac and Sanders’ results make intuitive sense. First, when it is lighter longer, criminals and the crimes they are committing are easier to spot, and thus more likely to be stopped. Second, lighter evenings increase foot traffic and consequently increase the number of possible witnesses that may be roaming the street at a given time. These outcomes hearken back to Munyo’s criminal incentives idea. The greater the cost present for criminal behaviour – one of which is the likelihood of being caught – the less likely the commission of a given offense.
Research conducted by Rebecca Umbach, Adrian Raine, and Greg Ridgeway found a 2.9% reduction in assaults immediately following the beginning of daylight saving time, and a 2.8% rise in assaults after the return to standard time in the fall.3 The majority of street crimes happen in the evening, between 5 and 8 PM, and more light later into these hours disincentivizes criminal activity during these high-crime hours due to increased visibility and foot-traffic. If crime rates fall in the evening due to it being lighter later, one could infer that crime in early morning hours would increase since it is darker. However, Doleac and Sanders find that this is not the case to any significant degree.4
There is no shortage of arguments that the practice of moving clocks forward and backwards for daylight saving time should be eliminated. It increases instances of car accidents, heart attacks, and various work injuries.5 In conjunction with these findings, it makes sense to choose either standard time or daylight saving time and stick with it. From a Criminal Law perspective, it would be best to choose daylight saving time. The commission of crimes is shown to be reduced by increasing the costs – both real and opportunity – of committing and offense, as well as increasing the likelihood that offenders will be seen and caught.
By permanently moving to, and sticking with, daylight saving time all year round, the evidence suggests that crime rates, accidents, workplace injuries, and heart attacks will all be reduced. That type of impact is not something to sleep on.
1 Daylight saving time and crime: Does tiredness also affect criminal behavior? by Ignacio Munyo.
2 Under the Cover of Darkness: How Ambient Light Influences Criminal Activity by Jennifer L. Doleac and Nicholas J. Sanders.
3 Aggression and sleep: a daylight saving time natural experiment on the effect of mild sleep loss and gain on assaults by Rebecca Umbach, Adrian Raine, and Greg Ridgeway.
4 Supra note 2.
5 Shifts to and from Daylight Saving Time and Incidence of Myocardial Infarction by Imre Janszky and Rickard Ljung; Daylight Savings Time and Traffic Accidents by Stanley Coren; Changing to Daylight Saving Time Cuts Into Sleep and Increases Workplace Injuries by Christopher Barnes and David Wagner