The Undercover Economist


Would the United States be better off with only one time zone?

The clocks go back tomorrow, which means an extra, delicious, guiltless hour in bed. Every year I dream of a world where the clocks go back every day. Of course, that would create trouble, notably that in two weeks’ time I’d be waking up after sunset. So, I toe the line and put the clocks back only once a year, and—sigh—put them forward again in the spring.

My annual inner monologue suggests two reasons to get up in the morning and go to bed at night: first, to enjoy the sunshine, and second, because that is what everybody else does. But what if the two imperatives collide? What matters more, waking up at the same time as everyone else or waking up with the sun? It might sound like a daft question, but not if you’re a Hong Kong-based journalist filing for a London-based newspaper or a financial analyst in Silicon Valley who needs to be awake when the market opens on Wall Street at 6.30 a.m. Pacific Time.

Coordination may be important not just for the global elite, but also for those who deal with them. If enough California financiers are going to work at 5:00 in the morning, the gas stations and coffee shops will start to open early, too: The baristas there don’t need to coordinate with the baristas in Manhattan, but the financiers provide a link that is powerful enough to make sure that they do anyway.

Any resident of Queensland in Australia can assure you of this. Queensland doesn’t switch to daylight-saving time when the other east-coast states do, but some Queenslanders simply get out of bed earlier in the winter to stay in sync. Or consider the states in northern Mexico, which align their time zones with the neighboring U.S. states rather than the rest of the country, even down to the idiosyncrasies of whether daylight-saving time is observed.

All that creates a problem. Not every Queensland resident synchronizes with the rest of the country, which means that neighbors will be out of sync with each other. The Californian demands that the barista rises early, which might also lead to demands for early rising by the barista’s wife, bus driver, nanny, or mailman. Perhaps it would be better for the United States and Australia to mimic China in having a single, unified time zone. That would get everybody in sync with each other, although not with the daylight. So, which is more important—coordination or sunlight?

Three economists, Daniel Hamermesh, Caitlin Myers, and Mark Pocock, have devised a way to find out how important these coordination effects really are relative to sunrise or to the official time. One of their tools is based on a historical relic: the fact that television schedules in the United States vary by time zone.

This practice originated in the 1920s, when the Eastern and Central time zones received simultaneous live radio broadcasts, with the Central time zone broadcast being an hour earlier on the clock. The sparsely populated Mountain and Pacific time zones had to listen to repeats instead. For no other reason than pure tradition, then, prime-time evening shows screen at 10 p.m. Eastern and Pacific, 9 p.m. Central and Mountain.

But then, take a state such as Arizona, which does not observe daylight-saving time. (Neither does the adjacent Mexican state of Sonoramore coordination.) In winter, Arizona keeps the same time as the other states in the Mountain time zone. In summer, it is on the same clock as the states of the Pacific time zone but with the evening shows still at Mountain times. * That sort of quirky setupthere are othersallows Hamermesh and his colleagues to show the impact of the television schedules on people’s daily routines.

Rather depressingly, David Letterman outshines the sun in his effect on what people are doing. Push the television schedules an hour later and 5 percent of people will be watching television later—nearly a third of those actually watching the television. But if sunset is an hour later (because the individual is at the western end of a time zone), only half of 1 percent of people will watch later television. The effect also spills over onto sleeping patterns: The television, more than the sunrise, determines when people get up in the morning.

That itself simply shows that people pay more attention to the television than to the great outdoors. But there is also a strong signal that coordination really matters, because the television schedules govern the behavior even of people who don’t watch television. Even those people who don’t know who David Letterman is live their lives to his schedule so that they can synchronize with a nation of TV-watchers. Perhaps the Chinese are right: Forget the sunrise and make sure, instead, that people are in sync with each other.

Correction, Oct. 30, 2006:There were two mistakes in the original article. First, the article originally implied that Arizona was in the Pacific time zone during daylight-saving time. Arizona remains in the Mountain time zone during daylight saving, but because it does not observe daylight saving, it is on the same clock as the Pacific states. Second, the article reversed the schedule for daylight-saving time. It occurs in the summer months, not in the winter months. (Return to the corrected sentence.)