A new study shows that the risk of fatal car crashes goes up on tax day.

Examining 30 years of road crash data from the National Highway Traffic Safety Administration, researchers led by Dr. Donald Redelmeier of the University of Toronto compared the number of fatal car accidents occurring on tax day (April 15 or whichever weekday that taxes are due), one week before and one week later. Their results show that 19,541 people were involved in fatal crashes on the 30 tax days — that's 404, or 6%, more than on the non-tax days the researchers studied.

The underlying causes aren't clear, but the researchers say it is likely human stress that's leading to extra deaths. "Stressful deadlines lead to driver distraction and short-term human error," says Dr. Redelmeier. "Other reasons could include sleep deprivation, inadvertent distractions and less tolerance towards hassles on tax day."

No one is immune to the tension that comes from filing taxes either. "Who looks to tax day in a joyful way? Even those who are getting refunds are stressed. Refunds are never as big as they thought and there is always the chance they could be reviewed at a later date," says Dr. Redelmeier.

It doesn't help that filing taxes in the U.S. is a particularly frazzling experience. "Filing individual tax returns is a big deal. The U.S. tax code is twice as long as Canada's and 10 times as long as France's. So for the average family of four, it amounts to about 40 hours of work each year, and a lot of people pack it up at the end. They don't spread out the work," Redelmeier says.

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