Are people in the Central time zone more productive because TV schedules let them sleep more?

September 27, 2013

Dear Cecil:

Until recently, television viewers were at the whim of network executives when it came to scheduling — most had to stay up until 11 PM to catch the full slate of prime-time programming. The exceptions were those in the Central time zone. Since network programming begins and ends an hour earlier there, viewers could get to bed sooner and get more shuteye. Since productivity is dependent on adequate sleep, are (or were) our mid-American brethren more productive than the night owls on the coasts, thanks to TV?

Cecil replies:

You’re thinking: Silly question. Even conceding that DVRs, streaming video, and other time-shifting advances have now freed countless viewers from the TV schedule's tyranny, so many things factor into productivity that trying to pin any differences on sleep variations is bound to be hopeless.

Sure enough, I haven’t been able to find any proof that the early-to-bed-early-to-rise folk in the middle of the country are noticeably healthier, wealthier, or wiser than those on the coasts. But you know what? Time-shifting technology notwithstanding, they do get more sleep.

To review the basics: In the days of radio, broadcasts in the Eastern and Central time zones were simultaneous (making nominal scheduled times in Central one hour earlier), shows were rebroadcast three hours later to the Pacific zone (making nominal scheduled times in Eastern and Pacific the same), and nobody worried much about the thinly populated Mountain zone. When TV arrived, it became customary for Mountain zone outlets to delay the New York feed for an hour (making nominal scheduled times in Central and Mountain the same). This practice persists today: prime time is from 8 till 11 PM in the Eastern and Pacific zones and from 7 till 10 in Central and Mountain, with some local variation.

How much do broadcast schedules affect the daily lives of people in different parts of the U.S.? It’s not like the entire day’s activities are offset by an hour in the middle of the country compared to the coasts — it’s fair to say lunchtime starts around noon all over.

But there are differences. In a 2006 study, researchers examined 35,000 time-use diaries of Americans collected by the Bureau of Labor Statistics over two years. Several variables were examined for their effect on sleep and work schedule, including sunset time, marital status, age, children, and occupation. There were some predictable variations: farmers tend to get up notably early, for example.

Here’s the interesting thing, though. Sunrise and sunset, which are determined by the rotation and axial tilt of the planet, for God’s sake, have minimal impact on Americans’ schedules, even taking nominal clock differences into account. The big factor is TV.

Overall, folks in the Central and Mountain time zones were around 4 percent more likely to be awake at 7 AM and 3.5 percent more likely to be at work by 8 AM — a significant but still fairly modest difference. The variance was more striking at night. At 11 PM local time, the researchers write, “people in the center of the country are 10 percentage points more likely to be asleep than people on the coasts.” A separate study found heartlanders got 15 minutes more sleep on average, proposing TV schedules as a likely cause.

To be clear, TV isn’t the only cue involved here. Work schedules, and in particular the need to coordinate with other parts of the country, also play a role. People in the Pacific time zone are around 5 percent more likely to be awake at 7 a.m. than those in the Eastern zone, no doubt because a lot of them have to be on the horn with people in New York who’ve been up for hours.

At night, however, TV rules. We’re often told Americans don’t get enough sleep; the obvious solution is to go to bed sooner. But on the coasts, where the choice is between catching a few more Zs, thereby improving your health, or watching one last show, people tend to choose TV.

How does this translate into productivity? Hard to say — while Easterners started work a little later than those in the Central time zone, researchers also found they were more likely to work over lunch, possibly erasing any productivity gap.

Fortunately — at least for the purposes of this column — we have Indiana. Until a 2006 law mandated daylight saving time statewide, three different time schemes were employed within its confines: most of the state's counties were on Eastern time but didn't observe DST, while others were on either Eastern or Central but did have DST, thus providing a unique laboratory for time zone research. One analysis of Indiana SAT results from 1997 to 2006 found a clear correlation between local time policy and students' scores, but didn't think the issue was Eastern vs. Central; it was that kids in DST counties scored lower. Never mind productivity — as the authors put it: “Starkly expressed, DST appears to cause brain damage.”

I respectfully suggest this conclusion needs to be revisited. If asked what’s most likely to cause brain damage: daylight saving time, watching TV, or living in Indiana, I ain’t going with DST.

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References

Basner, Mathias, and David F. Dinges. "Dubious bargain: trading sleep for Leno and Letterman." Sleep 32.6 (2009): 747-752.

Espinoza, J. Alberto et al. “Do Gradations of Time Zone Separation Make a Difference in Performance? A First Laboratory Study” International Conference on Global Software Engineering, Munich, Germany August, 2007.

Gaski, John F., and Jeff Sagarin. "Detrimental effects of daylight-saving time on SAT scores." Journal of Neuroscience, Psychology, and Economics 4.1 (2011): 44.

Hamermesh, Daniel S.; Myers, Caitlin Knowles; Pocock, Mark L. “Cues for coordination: light, longitude and Letterman” IZA Discussion Papers, No. 2060 (2006).

Olders, Henry. "Average sunrise time predicts depression prevalence." Journal of Psychosomatic Research 55.2 (2003): 99-105.

Silva, Graciela E., et al. "Relationship between reported and measured sleep times: the sleep heart health study (SHHS)." Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine 3.6 (2007): 622.

White, T. M., et al. "Incidence of winter depression varies within time zones." Society for Light Treatment and Biological Rhythms 17th annual conference. Eindhoven, the Netherlands. 2005.

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