Daylight Saving Time: Bad For Your Health, Not Good For Much Else
There's little benefit, and much cost, to moving our clocks back and forth every six months. So why do we do it?
It probably shouldn’t come as a surprise to learn that when you set your clock ahead before going to bed last night, it wasn’t necessarily good for your health:
Monday morning risks can be more serious than needing to nap at your desk: researchers at Loyola University School of Medicine report that there are more workplace injuries and traffic accidents the day after we turn our clocks ahead. Heart attack rates increase by as much as 10%. The time change is hardest on those who are chronically sleep deprived: the National Sleep Foundation estimates that more than one-third of Americans are dangerously sleepy.
While most people will adjust to the time change in a couple of days, night owls and those who habitually grab fewer than seven hours of sleep a night can take a full week to catch up.
As if that weren’t bad enough there’s absolutely no evidence that Daylight Saving Time results in reduced energy use:
Here’s a raft of studies on the subject. Most of them find that while households do use less lighting during daylight saving, thanks to the longer, brighter afternoons, they also end up cranking up the air conditioning more, which makes it either a wash or a net loser for energy use. A 2008 paper (pdf) by economists Matthew Kotchen and Laura Grant examined what happened in Indiana when, thanks to a change in state law, all counties suddenly had to shift to daylight saving.
The study found that, not just in Indiana, but nationwide, the change from Standard Time to Daylight Saving Time actually increases energy use:
The history of Daylight Saving Time (DST) has been long and controversial. Throughout its implementation during World Wars I and II, the oil embargo of the 1970s, consistent practice today, and recent extensions, the primary rationale for DST has always been to promote energy conservation. Nevertheless, there is surprisingly little evidence that DST actually saves energy. This paper takes advantage of a natural experiment in the state of Indiana to provide the first empirical estimates of DST effects on electricity consumption in the United States since the mid-1970s. Focusing on residential electricity demand, we conduct the first-ever study that uses micro-data on households to estimate an overall DST effect. The dataset consists of more than 7 million observations on monthly billing data for the vast majority of households in southern Indiana for three years. Our main finding is that—contrary to the policy’s intent—DST increases residential electricity demand. Estimates of the overall increase are approximately 1 percent, but we find that the effect is not constant throughout the DST period. DST causes the greatest increase in electricity consumption in the fall, when estimates range between 2 and 4 percent. These findings are consistent with simulation results that point to a tradeoff between reducing demand for lighting and increasing demand for heating and cooling. We estimate a cost of increased electricity bills to Indiana households of $9 million per year. We also estimate social costs of increased pollution emissions that range from $1.7 to $5.5 million per year. Finally, we argue that the effect is likely to be even stronger in other regions of the United States.
When Congress decided in 2005 to extend Daylight Saving Time by a month, one of the justifications cited for the move was the claim that it would reduce oil consumption by at least one percent because of the impact on driving habits. In 2008, a Department of Energy study [PDF] found that the move had no appreciable impact on gasoline consumption.
Additionally, the impact of the time change on the economy seems negligible at best:
Retailers love the extra sunlight — it means that there are more customers around who are willing to go out and shop. The all-powerful golfing industry is also a big fan, apparently. On the other hand, daylight saving can cut into sales for movie theaters and reduce the audience for prime-time television — people go out and enjoy the evening air instead of staring at screens inside.
Finally, one economist has calculated that the opportunity cost of Daylight Saving Time:
In 2008, economist William F. Shughart did a back-of-the envelope calculation and estimated that the opportunity cost of daylight savings time was $1.7 billion per year:
“Although it is unclear what benefit Americans derive from adjusting their timepieces twice a year, the costs they bear are clear. As the Benjamin Franklin adage goes: Time is money, and time spent resetting clocks and watches is time that cannot be devoted to other, more valuable uses. Switching between daylight saving and standard time has what economists call an ”opportunity cost.”
Economists typically value the opportunity cost of a person’s time at his or her wage rate. The U.S. Department of Labor’s Bureau of Labor Statistics reports that the average American’s hourly wage was $17.57 in September 2007. Assuming that it takes everyone 10 minutes to move all of their clocks and watches forward or backward by an hour, the opportunity cost of doing so works out to $2.93 per person. Multiplying that number by the total U.S. population (excluding Arizona) yields a one-time opportunity cost for the nation of just under $860 million—or, to be more precise, $858,274,802. Since clocks must be changed twice every year, this back-of-the-envelope calculation must be doubled, to approximately $1.7 billion annually.”
The only benefits that can conceivably attached to Daylight Saving Time would seem to be ones that cannot be quantified, such as the psychic benefit of having daylight last longer into the late afternoon/early evening, meaning that people have more time after normal work hours for outdoor activities. Today’s sunset here in Virginia, for example, is at
7:15pm rather than 6:15pm. By mid-April, we’ll have daylight until nearly 8pm. Is that a good thing? I suppose it is. Of course, if we just stayed on Standard Time, or for that matter made DST itself Standard Time it really doesn’t matter, we’d get longer days anyway since the days will become longer as we get closer to June 21st. Is there really all that much benefit from manipulating the clock every six months like this? I don’t really see it.
So there you have it. Moving the clocks ahead an hour, and then back again seven months later, is bad for your health, it increases the risk of road accidents, it increases energy use, and it has little if any real benefits to the economy or the environment. So, tell me again why we still have it?
Clock Showing Time Change image via Shutterstock