The mixed benefits of an extra hour

Gldburger | Getty Images

Don't forget to turn your clocks ahead this weekend, for the questionable annual tradition of daylight saving time is upon us.

Every year around this time, we're treated to a regular deluge of warnings about our health and productivity tied to the loss of an hour of sleep. But if there's one thing you should do, it's watch your portfolio for signs of a dropping market.

Since 2007, the S&P 500 dropped an average of 0.24 percent after a weekend of "spring forward." That's far more than the average 0.03 percent drop over non-time change weekends. That's from close of the markets Friday to close Monday, so any effect of the clock shift would be captured.

A study from 2000 showed a similar pattern of stock exchanges with significantly worse returns over the daylight saving weekend than other times during the year. The researchers argued that much of the drop could be attributed to traders' lack of sleep and the general disorder caused by the clocks' change.

"The magnitude of the daylight saving effect, roughly 200 to 500 percent of the regular weekend effect, is both statistically and economically significant in several international financial markets," the authors wrote. "In the United States alone, the daylight saving effect implies a one-day loss of $31 billion on the NYSE, AMEX and NASDAQ exchanges."

Daylight saving time originated as an energy-saving tool during World War I, according to some sources. The idea is that by adding an hour of daylight to days in half the calendar, Americans would use less fuel to light the night. Indeed, studies from the Department of Energy suggest a 0.03 percent drop in annual household energy usage thanks to daylight saving.

That might not sound like a huge drop, but it's enough to power about 122,000 homes for an entire year.

Golf and barbecue

Michael Downing, a Tufts professor and the author of "Spring Forward: The Annual Madness of Daylight Saving Time," has said the continued practice of daylight saving is largely thanks to businesses — in particular, the U.S. Chamber of Commerce, which supported DST whenever there's been a movement to curb it.

"The chamber understood that if you give workers more sunlight at the end of the day they'll stop and shop on their way home," Downing told WNYC.

Downing has cited the golf and barbecue industries in particular as proponents of daylight saving. Golf courses reportedly make an additional $400 million in annual revenue thanks to the extended hours.

But the flip side is that the lost hour of sleep can have detrimental effects, as illustrated with the market's performance. There's other research that shows the ill effects daylight saving has on health and well being, from increased strokes and heart attacks to lost productivity and workplace injuries.

A 2013 study put the total cost of all of this DST-related chaos at around $434 million. That's a big bite out of the economy for a little extra shopping and a few more tee times.