The Economics of Sleep, Part 2 (Rebroadcast)

People who sleep better earn more money. Now all we have to do is teach everyone to sleep better.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Stephen J. Dubner?

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• 1:27Stephen J. Dubner?

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• 1:54Stephen J. Dubner?

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• 2:35Stephen J. Dubner?

  So are you saying, right here and right now, that you bow from today going forward for one week, that you're going to do what? That you're going to put all your screens outside of the bedroom at a certain time, let's say? Is that what you're?

• 2:45Speaker 01

  Absolutely.

• 2:47Stephen J. Dubner?

  On last week's show, The Economics of Sleep, Part One, we talked to Lauren Hale. She's a sleep researcher at Stony Brook University. She told us that if you want to sleep well, you should avoid all screens for half an hour before going to bed. And yet, she doesn't.

• 3:02Speaker 01

  I admit, I use screens at bedtime. I should not, but screens are enticing and relaxing.

• 3:10Stephen J. Dubner?

  But she promised to give it a try. For one week, she would not look at a single screen. No TV, no computer, no smartphone, between 9:00 at night and 7:00 in the morning.

• 3:21Speaker 01

  The real challenge is try it for a week and see if you feel better, if you're sleeping more, if you're going to bed earlier, and see how you feel.

• 3:30Stephen J. Dubner?

  So how did it go?

• 3:32Speaker 01

  It went great. I was shocked at how many times I wanted to check my phone, turn on the TV, go to the computer, any number of screens, they were all yelling out to me. But I held back, and I slept so much better. I can hardly believe it.

• 3:51Stephen J. Dubner?

  Now, we should say that Hale is still fairly sleep deprived. She's got a newborn and she wakes up during the night to nurse him. But what was most surprising about her no-screen experiment was when she got more sleep. Usually, when she wakes up for a 5:00 AM feeding, she stays up and gets right on her phone, answering emails and checking out what her friends have been posting online.

• 4:11Speaker 01

  And the most interesting thing to me was I really expected that all of the gains in my sleep loss were going to come at the beginning of the night. Because when we look at teenagers, that's what we find. We find that kids and adolescents who use screens at night before bed, they go to bed later, they have a longer time until they fall asleep. And I expected the same with me. And I probably also experienced some of that. But the real benefits for me came in the morning, because I set that 7:00 AM screen time. And by forcing myself to stay away from screens after I do my morning nursing of my baby, I would just go right back to bed at 5:30 and sleep until he woke up at 7:00.

• 4:54Speaker 01

  And I tell you, for the last six months, I would usually stay up once I woke up at 5:30. So this was a huge benefit to me. For the last week, I've been getting at least an hour and a half more sleep, because I wouldn't allow myself to check email, or log on to Facebook, or do anything like that until at least 7:00 in the morning. I extended my sleep. Pretty amazing.

• 5:22Stephen J. Dubner?

  So, first of all, you're welcome, Lauren Hale. Plainly, I have a future as a sleep consultant. Let's see, what other sleeping problems should we be fixing? In last week's episode, we talked about the possible connection between poor sleep and poor health.

• 5:38Speaker 01

  Cardiovascular disease, there's associations with cancer.

• 5:43Stephen J. Dubner?

  We talked about how mushy sleep data can be, as it is often the result of self-reported surveys.

• 5:49Speaker 02

  One approach people in surveys unfortunately often resort to is just giving an answer which they think will be a well-accepted answer to the person interviewing them.

• 5:58Stephen J. Dubner?

  And we looked into the racial gap in sleep and the wealth gap.

• 6:02Speaker 03

  The answer is very, very clear. Those who earn more money per hour, who have better, what we call, in economics, opportunity cost of working, they sleep less.

• 6:14Stephen J. Dubner?

  We also asked you about your sleep routine.

• 6:18Speaker 04

  My name is Anne, and I cannot wear socks when I'm sleeping, or else I get really thirsty at night.

• 6:25Stephen J. Dubner?

  So this week, in The Economics of Sleep, Part Two, we get more heavily into the actual economics part, as in, what effect, if any, sleep has on how much money you make? Given what we've learned about mushy sleep data, how would you even begin to answer a question like that?

• 6:44Speaker 05

  What we really need is something like an experiment for sleep, almost as though we go out in the United States and force people to sleep different amounts, and then watch what the outcome is on their wages.

• 6:55Stephen J. Dubner?

  And, yes, we'll hear more of your sleep stories.

• 6:59Speaker 06

  I've actually been keeping a spreadsheet on my sleep.

• 7:03Speaker 07

  Eating dinner late actually improves my sleep quality.

• 7:08Speaker 08

  What do I wear?

• 7:10Speaker 08

  Butt naked, I think, is the American way of saying it.

• 7:25Speaker 09

  From WNYC Studios, this is Freakonomics Radio, the podcast that explores the hidden side of everything. Here's your host, Stephen Dubner.

• 7:42Stephen J. Dubner?

  Since most of us sleep away roughly a third of our lives, a third of our lives, that's nearly as much time as we spend with our screens, and surely, sleep has been the focus of a great deal of economic research, hasn't it?

• 7:55Speaker 05

  Economists have historically treated sleep as something to be ignored, something outside the realm of economics. People used to just subtract eight hours for sleep and then say, we're going to worry about the 16 hours that are left over.

• 8:08Stephen J. Dubner?

  That's Matthew Gibson. He is interested in the economics of sleep. When we spoke, he was finishing up his economics PhD at the University of California, San Diego.

• 8:18Speaker 05

  And I'll be an assistant professor of economics at Williams College beginning in the fall.

• 8:23Stephen J. Dubner?

  Okay, three things to say about that. Number one, congratulations, Professor Gibson. Number two, for any Williams students taking econ with Professor Gibson in the fall, he will probably be paying a lot of attention to whether you fall asleep in class. And number three, Gibson was intrigued by the economics of sleep, in part because so many brilliant and even radical economists had overlooked it.

• 8:46Speaker 05

  Gary Becker, famous University of Chicago economist who looked at the economics of everyday life, things like the economics of marriage, even a very open-minded economist like that would tend to look at sleep and say, well, when I think about time use, I'm going to ignore sleep. I'm going to concentrate on the decisions people make about the time when they're awake. How much leisure do they take and how much are they at the office?

• 9:08Stephen J. Dubner?

  But then along came Dan Hamermes.

• 9:10Speaker 05

  Hamermes was the first to take sleep seriously as part of a time use decision, to say, well, wait, if I'm a worker, sleep isn't just something I do automatically. I make choices about when I go to bed and when I get up, and those have effects on the other time uses I engage in: leisure, sports, television, work.

• 9:29Stephen J. Dubner?

  Hamermes is an economics professor, emeritus at the University of Texas, currently at Royal Holloway University of London. And how did he first get interested in sleep?

• 9:38Speaker 03

  This is a bit embarrassing. I was first interested in whether people who have higher wages and higher earnings opportunity engaged in less sexual activity or engaged in more quick sexual activity. And the sad fact was that in those data where they did have time diary, time on sex, sex was a very rare activity. I mean, these were either monks or nuns or liars, I don't know which. And for that reason, I said, well, let's think of something bigger, which is sleep, which in fact is the most common activity in terms of time spent that humans engage in.

• 10:16Stephen J. Dubner?

  In 1989, Hamermes and a colleague named Jeff Biddle published a paper called Sleep and the Allocation of Time. Using data from a Time Diary survey from 1975, they wanted to know if high-wage earners slept more or less.

• 10:32Speaker 03

  That was a crucial question, and we found, in fact, that they slept less, those who had better earnings opportunities.

• 10:39Stephen J. Dubner?

  The researchers found that for every extra hour that people worked, they slept roughly 10 fewer minutes per night. If you're an economist, you'd file this finding in the opportunity cost folder.

• 10:51Speaker 03

  Indeed, when this research was first written up in 1989, the headline was "Sleep: Why Bother? It Costs Too Much." And the argument being there that if you have other things to do with your time, like make money, you'll sleep less. The crucial point is sleep is not entirely biological. It responds to incentives. That's the interesting economic point.

• 11:13Stephen J. Dubner?

  There are, of course, limits. Sleep, being a biological imperative, can't simply be eliminated in pursuit of more money.

• 11:20Speaker 03

  We have a theory. It says sleep has a cost. It also has a benefit. In other words, at some point, even though I could be making a lot of money, the extra money doesn't matter very much to me. And if I don't sleep enough, it's going to wind up hurting my productivity and my eventual earnings ability. So one has to trade off these two things, one against the other. The net effect will be that the people with lots of opportunities will sleep less, but not so hugely less that they hurt those opportunities.

• 11:48Speaker 05

  When I have a poor night of sleep, I feel like a wreck.

• 11:51Stephen J. Dubner?

  That, again, is Matthew Gibson.

• 11:52Speaker 05

  I do believe it affects my performance. And also, I'm just frankly a much better human when I get eight hours than when I get six.

• 11:59Stephen J. Dubner?

  So Gibson takes sleep seriously. He gets to bed by 10 at night, wakes up at 6. He does use a smartphone, but not the way Lauren Hale used to use it.

• 12:10Speaker 05

  I have one of these goofy apps on the iPhone that plays rain sounds. I run that all night.

• 12:17Speaker 05

  I end up sharing rooms with other economists at conferences sometimes and there's always this awkward moment where I say, "Do you care if I play the iPhone rain sound tonight?"

• 12:27Speaker 05

  I think most people would be reluctant to reveal their true feelings. I usually get a funny look followed by a scent.

• 12:34Stephen J. Dubner?

  Gibson wanted to build off the Hammer Mesh research, showing that high earners sacrifice some sleep time, and answer a related question: How would getting more or better sleep affect your earnings? He teamed up with Jeffrey Schrader, another PhD candidate at UC San Diego. In a perfect world, they decided, they would run a giant sleep experiment.

• 12:57Speaker 05

  Almost as though we go out in the United States and force people to sleep different amounts, and then watch what the outcome is on their wages. And it turns out that ever since we've put time zones into place, we've basically been running just that sort of giant experiment on everyone in America.

• 13:13Stephen J. Dubner?

  And you thought that time zones were actually useful somehow. Well, they are, but Gibson and Schrader realized their experimental value, too. First, a quick primer on American time zones.

• 13:25Speaker 05

  So if you do what everyone does, and go first to Wikipedia, it will tell you all about Railroad Standard Time, which was instituted in the US in 1883. And once the railroads got on this bandwagon, the federal government rather quickly followed.

• 13:41Speaker 05

  Before that, each local area kept its own idiosyncratic time. So if you journeyed any appreciable distance and showed up in the town square, it might have behooved you to look at the clock outside the bank or the clock on the town hall to say, "Hey, what time is it for people in this town?"

• 13:57Stephen J. Dubner?

  Today, there are four time zones in the continental US: Eastern, Central, Mountain, and Pacific. And in each one, sunset happens roughly one hour earlier in the eastern edge of the time zone than the western edge. Consider two places like Huntsville, Alabama, which is near the eastern edge of the central time zone, and Amarillo, Texas, near the western edge of the central zone.

• 14:18Speaker 05

  Amarillo is the birthplace of my illustrious co-author, Jeff Schrader.

• 14:21Stephen J. Dubner?

  So even though Amarillo and Huntsville share a time zone, the sun sets about an hour later in Amarillo, according to the clock. And since the two cities are at roughly the same latitude as well, they get roughly the same amount of daylight, too. Just to make sure we had this right, we called the mayor of Huntsville Tommy Battle. This was back in May.

• 14:42Speaker 10

  Usually sunset is around 7:30 right now.

• 14:46Stephen J. Dubner?

  By the height of summer, sunset would be close to 8 o'clock. Whereas over in Amarillo, some 900 miles west of Huntsville, well, we couldn't get hold of the mayor there, so we called another Amarilloan Marcia Schrader.

• 14:59Speaker 11

  I am the mother of Jeffrey Schrader, who is studying economics at the moment.

• 15:05Stephen J. Dubner?

  Schrader, you'll remember, is Matthew Gibson's co-author.

• 15:09Speaker 11

  And I live in Amarillo, Texas. We get a lot of sunshine here. The sun rises very, very early and sets around 9 o'clock, maybe a few minutes before 9.

• 15:20Stephen J. Dubner?

  So you've got two cities on either end of a time zone, roughly the same size, just under 200,000 people each, where, according to the clock time, sunset is an hour apart. Now, what good is that to a pair of economists interested in sleep research?

• 15:39Speaker 05

  Well, it turns out that the human body, our sleep cycle, responds more strongly to the sun than it does to the clock. So people who live in Huntsville and experience this earlier sunset go to bed earlier.

• 15:52Stephen J. Dubner?

  And the people of Amarillo go to bed quite a bit later. You can see this in data from the American Time Use Survey.

• 15:59Speaker 05

  If we just plot the average bedtime for people as a function of how far east they are within a time zone, we see this very nice, clean, straight line with earlier bedtime for people at the more eastern location.

• 16:14Stephen J. Dubner?

  Now, this is purely anecdotal, but Mayor Tommy Battle in Huntsville says this sounds about right.

• 16:21Speaker 10

  I'm an early to bed person. I'm 9:30 to 10:00, I'm in bed.

• 16:25Stephen J. Dubner?

  And Marcia Schrader in Amarillo.

• 16:28Speaker 11

  Normally, I will get to bed by midnight or a little bit before midnight. Just the last couple of weeks, I can't make myself go to bed before 2 o'clock in the morning.

• 16:38Stephen J. Dubner?

  But since Huntsville and Amarillo are in the same time zone, people start work at roughly the same time, which means alarm clocks go off at roughly the same time.

• 16:49Speaker 05

  That means if you go to bed earlier in Huntsville, you sleep longer.

• 16:54Stephen J. Dubner?

  Gibson and Schrader found a significant difference in sleep duration between Huntsville and Amarillo.

• 17:01Speaker 05

  If I dose you, the person in Huntsville, with a one-hour-earlier sunset time, how much more do you sleep? And the answer is something like an hour per week. And this is what I mean when I say it's like we've been running a giant experiment. We've effectively been giving different locations in America different bedtimes based on where they are east to west within a time zone.

• 17:22Stephen J. Dubner?

  Gibson says he found the same effect in all time zones in the US, and it's been identified in other countries, including Germany.

• 17:29Speaker 05

  The question then is, does that have any impact? We have this variation in sleep that is clean, that is like an experiment, but does it actually change economic outcomes? If I compare the wages of people in Huntsville to wages of people on the western edge of the time zone, what change in wage does that difference in sunset produce?

• 17:49Stephen J. Dubner?

  So now Gibson and Schrader plugged in wage data for Huntsville versus Amarillo and other pairs of cities that had a similar sleep gap.

• 17:57Speaker 05

  And we find that permanently increasing sleep by an hour per week for everybody in a city increases the wages in that location by about 4.5%.

• 18:08Stephen J. Dubner?

  4.5%, that's a pretty good payout for just one extra hour of sleep per week. If you get an extra hour per night, Gibson and Schrader discovered. Here, let me quote you their paper. "Our main result is that sleeping one extra hour per night, on average, increases wages by 16%, highlighting the importance of restedness to human productivity." 16%, really?

• 18:33Speaker 03

  That seems huge to me.

• 18:34Stephen J. Dubner?

  That's Dan Hammermesh again. He read an early copy of the paper.

• 18:38Speaker 03

  I thought it was huge when I saw it, and I really wonder about that. It just seems too, too big, much too big, that to be credible.

• 18:47Speaker 05

  I think that's a reasonable reaction, right? We all have some prior number floating around our heads about what that number should be. And for me, and for most people to whom I've spoken about this paper, that 16% number is quite high.

• 19:02Stephen J. Dubner?

  High enough that if all else were equal, you might think about moving to a place like Huntsville if you lived in a place like Amarillo, because you'll get more sleep and make more money. For what it's worth, the median income in Huntsville is substantially higher than in Amarillo, although it might be reckless to pin that whole difference on sleep. We did ask Marsha Schrader in Amarillo what she made of her son's findings.

• 19:25Speaker 11

  I'm terribly disappointed and feeling very ripped off. I think Amarillo's per capita income is rather low on the national scale, but I never would have thought it was anything correlated with time zone. That explains a lot. I never earned more than $20,000 as a teacher.

• 19:46Stephen J. Dubner?

  The paper does note, however, that with higher incomes in a city come higher real estate prices. As they write, "Our wage effects are fully offset by increased home prices."

• 19:59Speaker 05

  And so workers don't have an incentive to move in response to those sunset doses.

• 20:04Stephen J. Dubner?

  That said, Gibson was surprised by the magnitude of their results. A 16% income boost from one more hour per night of sleep. That's a bigger boost than you'd expect from one additional year of education. But if you start feeling skeptical, he says, just think about the huge negative effects from sleep deprivation.

• 20:25Speaker 05

  So, beginning about 10 or 15 years ago, we started to see experiments in medical school where they would subject people to levels of sleep that are closer to real-world sleep deprivation, six hours a night, maybe four hours a night, for periods from seven to 21 days, one to three weeks. And they found very, very large effects on task performance, on these lab-type of tasks.

• 20:47Speaker 12

  Right away, you see the cognitive effects. David Dinges is a professor of psychology and psychiatry at the University of Pennsylvania. Attention becomes unstable. We have trouble thinking fast. Cognitive processing speed is markedly reduced. Short-term memory begins to fail. We can't hold things in our memory as well as when we're fully alert. Dinges and his colleagues have conducted several important sleep trials over the years. The less sleep we gave people at night, so if we went from seven or eight hours a night down to six or five, the more we got this cumulative rate of buildup of these deficits. They got worse every day. When the sleep got very short, down to four hours or three hours, they got worse every day, very rapidly and very dramatically.

• 21:31Speaker 12

  So there was a dose-response function. The less sleep you got chronically, the more rapidly you deteriorated. So the two things you see first are: you cannot sustain attention for very long. You try to compensate by then becoming impulsive. So what happens, paradoxically, with chronic sleep restriction is people will be slow to respond or lapse, and then they'll be overly impulsive and maybe talk or interact a lot, and then suddenly be out of it again. And that instability in attention is the hallmark of sleep loss, but very close behind it and equivalent to it is your cognitive processing speed. You simply cannot think as fast and solve a problem as quickly when you're sleep deprived as when you're not sleep deprived.

• 22:14Speaker 12

  So you can think of a number of ways that lack of sleep could translate into working worse, or working more sloppily, or less productively, and add up to such big income gains for people who sleep more.

• 22:28Stephen J. Dubner?

  Matthew Gibson again.

• 22:29Speaker 05

  One reason in all likelihood that it's big is it reflects these spillovers across workers, the fact that if you're more productive and we work in the same office, you help make me more productive. There also may be some really long run effects on how places develop because of the permanently higher sleep in a location. So you might think, for example, if you own an IT company and you're at the eastern edge of a time zone, your workers are permanently more productive because they sleep more. That might lead you to invest more in computers with which those workers can produce goods or services.

• 23:10Stephen J. Dubner?

  Okay, so there's pretty compelling evidence that an extra measure of sleep can pay off. But coming up after the break, if you're going to get, say, seven hours of sleep, does it matter when you get them? We look at some research that suggests the early bird really does get the worm.

• 23:28Speaker 13

  You could call it the premium for getting up early in the morning.

• 23:32Stephen J. Dubner?

  But first, as promised, here are some of your sleeping habits.

• 23:37Speaker 14

  My name is Spencer Rothfuss. I'm 16 years old and live in Omaha, Nebraska. I sleep fully dressed in the next day's clothes, so I'm ready to go in the morning.

• 23:45Speaker 08

  My name is Mark Allen. I'm calling from North Queensland in Australia. What do I wear? Butt naked, I think, is the American way of saying it.

• 23:53Speaker 06

  Hi, my name is Alexandra Nicholas, and currently I am based in Montgomery, Alabama. I've actually been keeping a spreadsheet on my sleep, which is super nerdy. But I have times when I went to sleep, when I woke up, when I actually got out of bed, how many alarms were required to make me get out of bed.

• 24:13Speaker 07

  Hi, my name is Adam Hill, and eating dinner late actually improves my sleep quality.

• 24:20Speaker 10

  I'm Tommy Daddel, mayor of the city of Huntsville, Alabama. Been mayor for seven years now, and all my habits are my wife's habits because she turns on the fan, and I never would have a fan on. But she also has it down to about meat locker temperature in the room, and I cover up real heavy.

• 24:37Speaker 15

  This is Rebecca Miller, and I live in Pleasant Grove, Utah. In high school or college, I would work the graveyard shift. And so I would sleep in a closet sometimes and wrap a shirt around my head so that I would convince my body that I was sleeping at night when really it was the daytime. My name is Keisha Walchmidt, and I have always been teased that I look like I'm dead when I'm sleeping. I sleep on my back with my arms folded across my chest, straight as an arrow.

• 25:15Stephen J. Dubner?

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• 25:58Stephen J. Dubner?

  Download the Quince app for app-exclusive offers or go to quince.com/freak. Get free shipping on your order and 365-day returns. Now available in Canada and the UK, too. That's Q-U-I-N-C-E dot com slash freak. Freakonomics Radio is sponsored by Southern New Hampshire University. There's no hiding how convenient Southern New Hampshire University makes college. They offer over 80 career-focused graduate programs online. Classes have no set meeting times, so you can balance life and learning, and online tuition rates are some of the lowest in the country, making it all a little more manageable. A school this willing to work with you is worth the investment.

• 26:42Stephen J. Dubner?

  Visit s n h u dot e d u slash Freakonomics to learn more.

• 26:51Stephen J. Dubner?

  Freakonomics Radio is sponsored by PNC Bank. Boring. Great word, bad rep. Yet, time and time again, here at Freakonomics, we find that when something culture-changing happens, boring things like calculations and careful planning are usually behind it. Which begs the question, why not apply it to other aspects of life? Like banking, for example. Well, PNC Bank did, since its inception, proving time and again that the best banking strategy isn't the exciting type, but the steady, reliable, definitely-not-YOLO type. PNC Bank: brilliantly boring since 1865. Brilliantly boring since 1865 is a registered mark of the PNC Financial Services Group, Inc. PNC Bank, National Association, Member FDIC.

• 27:45Speaker 16

  Good morning. Hello. This is your daddy.

• 27:49Stephen J. Dubner?

  Are you a morning person?

• 27:51Speaker 16

  Good morning. Good morning. Good morning.

• 27:55Stephen J. Dubner?

  Do you greet the day with a smile, ready to get things underway?

• 27:58Speaker 16

  What do you want to do? Daddy, I want to eat that.

• 28:03Stephen J. Dubner?

  That's Camille, two years old, and her father, Christopher Worth. He's one of the producers on our show. Camille likes to get up around 6:00 a.m.

• 28:11Speaker 16

  Yay!

• 28:13Stephen J. Dubner?

  Dad wouldn't mind getting up a little bit later.

• 28:15Speaker 16

  Ooh, big yawn.

• 28:18Stephen J. Dubner?

  But let's face it, getting up early is good training for the rest of your life. School, work, all those things that start in the morning.

• 28:27Speaker 13

  Society is structured in a way that it favors morning-type people more than evening-type people.

• 28:34Stephen J. Dubner?

  That's Jens Banke. He's an economist and a senior researcher at the Rockwell Foundation in Copenhagen. He studies things like time use and family economics. If you are a night owl, he says, staying up late and getting up late, it can feel like the world with its morning start times is against you.

• 28:54Speaker 13

  And for that reason, I said, well, if the morning-type people are favored, they might also be more productive and they might earn more than evening-type people.

• 29:06Stephen J. Dubner?

  In other words, after reading the work of Dan Hamermes and others about how the amount of sleep we get has an economic effect, he wondered about the effect of when you sleep.

• 29:16Speaker 13

  And that was what I decided to investigate. And my assumption was that there might be a relationship between when you sleep and how much you earn.

• 29:29Stephen J. Dubner?

  First, he needed to separate the population into early birds and night owls. The ideal way to do that, he decided, would be to map everyone's genes. Banke says we all have a distinct gene that influences our chronotype, that is, a given person's proclivity for waking up early or late. But it would have been way too expensive to gene map the entire population of Denmark, which granted is pretty small, about five and a half million people. So he turned to a Danish time use survey that covers more than 10,000 people, a rather exhaustive time use survey.

• 30:04Speaker 13

  We have a lot of information on every day in this country here.

• 30:09Stephen J. Dubner?

  One issue with sleep data is that when people wake up during the week isn't necessarily representative of their true chronotype. Even night owls have to get up for work.

• 30:18Speaker 13

  So what I did was to say, well, what happens to people during the weekend?

• 30:24Stephen J. Dubner?

  On the weekend, he figured, your true sleep nature emerges. Early birds would still get up relatively early, and night owls would revert to staying up late and sleeping late. Once he was able to separate the early birds from the night owls in the data, he compared their incomes.

• 30:40Speaker 13

  There was a significant differential in the sense that the morning type people earned four or five percent more than evening type people.

• 30:48Stephen J. Dubner?

  Four to five percent more for the early risers. And that's controlling for family background, education level, and so on. Banke believes the reason for this is pretty simple. If you're a morning person, you wake up on time feeling rested, since your body naturally told you to go to bed earlier. He found that early risers get a bit more sleep overall. Night owls, meanwhile, spend their lives sort of posing as early birds, getting up early because they have to, but staying up late because that's what their chronotype dictates. And that doesn't seem fair, does it? To get punished in the workforce because of your night owl genes? So what should be done? Banke argues that more flexibility in the workplace, even in the very pace of the day, would be a big help.

• 31:33Stephen J. Dubner?

  The good news is that, in Denmark at least, that's been happening. Danish companies used to enforce strict office hours, and Danish law used to prevent a lot of businesses from being open when a lot of people might like them to be open.

• 31:47Speaker 13

  You couldn't do shopping in most places after 2 PM on Saturdays, until Monday morning. And at most workplaces, you had to be there from 8 o'clock in the morning to 4 o'clock in the afternoon.

• 32:04Stephen J. Dubner?

  But that's been changing. Employers are more flexible. Shopping laws have been liberalized, all of which makes it easier to be a night owl. And Banke claims to have found evidence in the data that this really has paid off for night owls. Remember, he recently found that early birds make 4% to 5% more than night owls. He compared this result with the same data from 10 years ago.

• 32:26Speaker 13

  And there I could see that the premium for getting up early has decreased considerably over this period.

• 32:34Stephen J. Dubner?

  A decade ago, early birds earned 10% to 12% more than night owls. So the payoff for getting up early, or if you prefer to look at it from the other side, the penalty for being a night owl, has more than halved in a relatively short time. This trend, that increased flexibility in society helps certain people prosper, might explain another finding in his data, that the wage difference between early and late risers is higher for men than for women.

• 33:03Speaker 13

  The fact is that, at least at the Danish labor market, but probably on most labor markets, many more women have flexible working hours and part-time work. So they can find a more appropriate time of the day to work than it's impossible for men.

• 33:24Stephen J. Dubner?

  So there would seem to be compelling evidence on a lot of dimensions that sleep really matters for how much we earn, how we make decisions, how we feel, and in the long run, how long we live. If you live in a rich country like the United States or Denmark, it's natural to think about how sleep can help us improve a few percentage points here and there. But think about how big the sleep gains could be in a developing country.

• 33:53Stephen J. Dubner?

  This is Chennai, the sixth largest city in India.

• 33:57Speaker 17

  Which actually means it's huge. It's actually bigger than Chicago or LA. So it's a lot of people packed into a fairly small space.

• 34:06Stephen J. Dubner?

  Heather Schofield is a development economist with the Center for Global Development in Washington DC, and she's at the University of Pennsylvania. These days, she spends much of her time in Chennai.

• 34:17Speaker 17

  And everybody honks a lot because it's kind of a way of telling people where you are on the road and that you're coming. So it's pretty much constant auto horns all the time.

• 34:25Stephen J. Dubner?

  So you can imagine that sleep conditions in Chennai, with a lot of density, noise, poverty, are not quite optimal. Schofield says that a lot of families live in nothing more than an eight by 10 foot room.

• 34:37Speaker 17

  So there will be three or four other people in this eight by 10 room with you trying to sleep at night. Anytime anyone rolls over, they probably wake up everybody else. It's incredibly hot. Chennai is a city where the average high temperature is 90 to 95 degrees throughout the entire year. There's no air conditioning. Maybe there's a fan if you're lucky. You're probably sleeping on a hard concrete floor. Most likely, you don't even have a mattress or a pillow because it's hard to afford those goods. In addition, it's probably very loud. There are dogs barking, there are auto horns going at all hours. And if that weren't enough to make it really hard to sleep, there are probably mosquitoes there as well. It's a very tropical climate, so they're in there buzzing around your head, biting you, making you itchy. It's actually, it's just an incredibly difficult environment to sleep in.

• 35:23Stephen J. Dubner?

  Development experts have been trying to help poor countries for decades. The sexiest prescriptions are often big, complicated, top-down projects. More recently, nutrition and education have been in vogue.

• 35:36Speaker 17

  These other things like sleep, which somehow just haven't kind of entered into the popular belief as being important, maybe because it's not obvious that the poor would sleep worse, or maybe because it's not kind of immediate that it actually has these productivity effects, which is exactly why we're trying to study it and really understand what those implications are.

• 35:55Stephen J. Dubner?

  Okay, so, how do you study that? Schofield and her colleagues are currently running a randomized controlled trial in Chennai with about 250 people. They all work in jobs that require repetitive data tasks.

• 36:09Stephen J. Dubner?

  Schofield wants to learn if improving their sleep will help them earn more money.

• 36:13Speaker 17

  Basically, we'll conduct a lottery, and half the people in the study will be given things to help them sleep better at night. So we'll give them a mat to sleep on, something like a camping mat, which makes the surface softer. We'll give them a pillow so their neck isn't as stiff. We'll give them a light sheet and a fan to help keep the mosquitoes away. They'll also get an eye shade and earplugs to help deal with the light and the noise. In addition to that, we'll also ask them to take a nap in the office every day. They have that choice whether or not they want to, but there will be a very pleasant environment where they can go and it's cool and comfortable, and can take the 20 or 30 minutes just to rest. Because there's actually pretty good evidence from work here in the US and in other developed countries that short naps of 20 or 30 minutes could actually really improve your cognitive

• 36:58Speaker 17

  performance and your ability to kind of focus.

• 37:02Stephen J. Dubner?

  Running this experiment with people who do data entry for a living makes it pretty easy to measure any change in productivity.

• 37:07Speaker 17

  So we can see everything that you do in doing your work. Are you, how many data points are you entering? When are you doing them? How quickly are you doing them? How accurate are you? And your work is compensated according to how much and how well you do. So if people improve their work, either in terms of quantity or quality, that'll actually play out in their earnings. We'll see their earnings increase as well.

• 37:30Stephen J. Dubner?

  It's too early to tell what this research will yield. But to Heather Schofield, experimenting with sleep was a no-brainer. She used to see people she knew, rickshaw drivers who'd been involved in earlier studies, for instance, falling asleep in the broiling sun.

• 37:45Speaker 17

  If people are tired enough to be sleeping in the middle of the street in the 100-degree heat with trucks going by, it's pretty hard for them to be kind of as productive as possible in the labor force. So, you know, if we can help improve their sleep, our hypothesis is that it will actually very much improve their ability to both work longer and work harder and work better, you know, improve their performance on the job in quite a variety of different ways, and more broadly, to just improve the choices that they're able to make.

• 38:15Stephen J. Dubner?

  Doing this research has made Schofield more aware of her own sleep deficits. She's constantly flying back and forth between India and the US, and how hard it can be to get enough sleep.

• 38:25Speaker 17

  It's this constant battle, because I know from all the stuff that we're, you know, we're doing and all the research we're reading from other people that tells you all these things, the cognitive costs that it come with, that I should be doing so much better on. But it's also a constant tension. You know, it's one of those things that there's a lot of other constraints on your time, and so I'm very aware of it, but it doesn't always make it easy to change.

• 38:50Speaker 17

  But I've also realized there are a lot of things potentially I could do to help myself sleep better at night, even if I'm not going to spend more time in bed.

• 38:56Stephen J. Dubner?

  For example, she bought a pair of high-end earplugs and learned the best technique for putting them in.

• 39:03Speaker 17

  This is going to sound ridiculous, but imagine reaching your opposite arm over your head and then pulling up on your ear while you put the earplug in. That actually helps expand the ear canal a little bit, so that the earplug actually gets kind of well-settled in there when it expands and fills the space, so it actually blocks the noise much more effectively.

• 39:24Stephen J. Dubner?

  Oh my goodness, that works great. I also happen to wear earplugs when I sleep. I don't want to chance my eight hours to some random garbage truck or car alarm. So thanks for the earplug tip, Heather. For some more sleep tips, we turn to Dan Pardee.

• 39:41Speaker 18

  I'm the CEO of a company called Dan's Plan.

• 39:43Stephen J. Dubner?

  Dan's Plan is a sort of health consultancy in Northern California. Pardee does research with some scientists and he works with a lot of people who are trying to optimize their sleep. For just about everyone, the goal is pretty simple.

• 39:57Speaker 18

  So you want to wake refreshed and feel alert all day, every day. Cool, how do I do that?

• 40:01Stephen J. Dubner?

  He recommends that you start with a personal sleep experiment.

• 40:04Speaker 18

  So instead of waking by an alarm clock or by any sort of external means, you want to give yourself enough time in bed to wake upon its own volition. So the body wakes itself up and not by something else. And see, you know, how much time is that? See how much time you need on average. Write it down. And having that number, that time in your mind clearly established, is a very, very good thing.

• 40:28Stephen J. Dubner?

  You need to do this for a few weeks. And now you can start planning for how long you need to spend in bed. Consistency is important.

• 40:35Speaker 18

  And so if you're used to going to bed at midnight and getting up at eight, your body is primed to get really robust REM sleep around four, four, five, six in the morning. And so when you shift that, then you're not going to get as good of sleep as you would like.

• 40:50Stephen J. Dubner?

  If you're not sleeping well, if you find yourself exhausted during the middle of the day, Pardee thinks this may be caused by how you are receiving and processing light.

• 41:00Speaker 18

  So light is very important for our health. Light enters into the eye and it will communicate with a part of the brain, not the visual cortex, but another part of the brain that is referred to as the master clock. The scientific name is the suprachiasmatic nucleus. It's in the hypothalamus. And that part of the brain is keeping track of what time of day it is to say, okay, it's this time of day, do this type of activity. And so all of the body runs on these clocks, so it knows what to do when. 200 years ago, 90% of the United States was agrarian. So we were outside all day, tilling the fields, getting a lot of sun exposure. And then as the sun went down, the tone and the intensity of light would change.

• 41:42Speaker 18

  And that stimulates some darkness hormones, which facilitate the occurrence of sleepiness, which can then, you know, ushers in sleep. So now, we spend 90% of our time indoors. That's a huge shift. And the intensity of light indoors is surprisingly different than the intensity of light outdoors.

• 42:03Stephen J. Dubner?

  The result is that we often don't get enough light during the day, but paradoxically, too much at night.

• 42:09Speaker 18

  Now, we can artificially manipulate our light environment in the evening, and that's through room light and high-definition televisions and screens. And then that gives a daytime signal to the brain at night. And what ends up happening is those rhythms then become desynchronized. And we're basically creating a state of minor perpetual jet lag by the way that we live, by having mistimed lighting.

• 42:33Stephen J. Dubner?

  So what you want to do, Pardee says, is resync those rhythms. How does he do it? He has stopped wearing sunglasses. He gets outside as much as he can, even if it's just to make a phone call. And at night, he keeps the lights dim. He also wears a special pair of yellow-tinted glasses that filter out the kind of blue light that's emitted by artificial lights, including screens.

• 42:55Speaker 18

  And what that means is that I can see, but I'm not telling my brain that it's day. And the reason of that is when blue light is entering in the eye, it'll suppress the release of melatonin. And most people know melatonin as a sleepiness hormone. It's actually a darkness hormone. It has a modest soporific or sleep-inducing effect, but it's not very strong. But what it does is it tells the body that it's night. And the big benefit of that is I wake up much more refreshed the next day. I am ready to go, and I function pretty well all day long.

• 43:30Stephen J. Dubner?

  He makes it sound so easy, doesn't he? Of course, none of this takes into account the horn honking of Chennai, or that ready-to-go two-year-old, or any of the other sleep interrupters that all of us encounter.

• 43:46Speaker 19

  My husband's not in town, and I never...

• 43:51Speaker 19

  I never sleep well when he's not here.

• 43:53Stephen J. Dubner?

  But it's nice to see that people like Dan Pardey, and Heather Schofield, and Matthew Gibson, and Lauren Hale, are treating sleep so seriously. It's interesting. As obsessively as we measure so many things in society, especially our outcomes, health, wealth, education, productivity, we seem to spend a relatively small amount of time and effort really trying to understand how the inputs, the things that we control, affect those outcomes. Yeah, there are a lot of things beyond your control. But in terms of what you eat and drink, in terms of what kind of activities you do or don't do, and in terms of how much you sleep, well, those are in your hands alone. And after hearing from all these sleep experts the past two episodes,

• 44:38Stephen J. Dubner?

  I'm convinced we'd all be better off if we paid a little bit more attention to sleep, learned about it, and thought up ways to help more people get more of it and better quality sleep. If we find out that engaging with your smartphone 30 minutes before bedtime really is that bad, well, let's just shut off the internet every night at 11. How's that? All right, that's probably not a very good solution. When I think of famous sleep aids in history, I think of the Goldberg Variations, which to my mind is one of the most sublime pieces of music on the planet. They were written by Bach purportedly as a commission from a Russian ambassador who had trouble sleeping, and he wanted some sophisticated lullabies to be played by his personal keyboardist, Johann Gottlieb Goldberg,

• 45:23Stephen J. Dubner?

  right outside the ambassador's bedroom. Now, these facts have been disputed, but it is hard to dispute the quality of the Variations themselves, especially when played by someone like Glenn Gould.

• 45:36Stephen J. Dubner?

  So perhaps the least we could do in our collective pursuit of better sleep is require that, from this day forth, every podcast episode in the world shall conclude with a bit of the Goldberg Variations.

• 46:11Stephen J. Dubner?

  Hey. Sorry to wake you, but I wanted to tell you what to expect on the next Freakonomics Radio. We'll do the math on the payday loan industry.

• 46:22Speaker 20

  At first, it seems like easy money, but the average borrower ends up spending about 200 days out of the year in debt.

• 46:30Stephen J. Dubner?

  Are payday loans as evil as President Obama says? You can find out next time. All right. I'll shut up now. Sweet dreams.

• 46:57Stephen J. Dubner?

  Freakonomics Radio is produced by WNYC Studios and Dubner Productions. This episode was produced by Christopher Wirth and mixed by Andrew Dunn and Merritt Jacob. Our staff also includes Irva Gunja, Jay Cowett, Greg Rosalsky, Kasia Mahalovich, Alison Hockenberry, and Caroline English. You can find all our previous episodes at Freakonomics.com. You can also subscribe to this podcast, which I hope you will do, on iTunes or wherever you get your podcasts.

• 47:46Stephen J. Dubner?

  Freakonomics Radio is sponsored by EverPure. Is the value of AI not living up to the promise? The problem is probably your data, not your AI models. When it's scattered across different systems, getting your data AI-ready is a challenge. You keep your AI waiting, and everything slows down. EverPure unifies your data so you can see it, understand it, and control it all from one simple place and get it AI-ready fast. Unlock the true value of your AI at everpuredata.com.

• 48:18Stephen J. Dubner?

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• 49:03Stephen J. Dubner?

  So they are looking ahead and investing $80 billion in infrastructure upgrades and are committed to fueling growth in ways that benefit all customers so that reliable and affordable energy is accessible for generations to come. Go to southerncompany.com to learn more. Southern Company, building the future of energy.

• 49:26Speaker 21

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