The Economics of Sleep, Part 2

Stephen J. DUBNER: Are you saying, right here and right now, that you vow from today going forward, that 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…?

Lauren HALE: Absolutely.

On last week’s show — “The Economics of Sleep, Part 1” — 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.

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

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 nine at night and seven in the morning.

HALE: 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. See how you feel.

So how did it go?

HALE: 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 as they were all yelling out to me. But I held back. I slept so much better I can hardly believe it.

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 a.m. feeding, she stays up and gets right on her phone, answering e-mails and checking out what her friends have been posting online.

HALE: 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. I expected the same of me. I probably experienced some of that. But the real benefits for me came in the morning because I set that 7:00 am screen time. 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. I’ll tell you, for the last six months, I would usually stay up once I woke up at 5:30. 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.

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.

HALE: Cardiovascular disease. There’s associations with cancer.

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

Diane LAUDERDALE: 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.

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

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

We also asked you about your sleep routine:

Anne HILDEBRAND: My name is Anne. I cannot wear socks when I’m sleeping or else I get really thirsty at night.

So this week, in “The Economics of Sleep, Part 2,” we get more heavily into the actual economics part, as in what effect, if any, sleep has on how much money you make. Now, given what we’ve learned about mushy sleep data, how would you even begin to answer a question like that?

Matthew GIBSON: What we 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.

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

Alexandra NICOLAS: I’ve been keeping a spreadsheet on my sleep.

Adam HILL: Eating dinner late improves my sleep quality.

Mark ALLEN: What do I wear? Butt-naked is the American way of saying it.

*      *      *

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 — then surely sleep has been the focus of a great deal of economic research. Hasn’t it?

GIBSON: 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.”

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

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

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.

GIBSON: 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, “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? How much are they at the office?”

But then, along came Dan Hamermesh.

GIBSON: Hamermesh was the first to take sleep seriously as part of a time-use decision, to say, “Wait. If I’m a worker, sleep isn’t something I do automatically. I make choices about when I go to bed and when I get up. Those have effects on the other time uses I engage in; leisure, sports, television, work.”

Hamermesh 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?

HAMERMESH: 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 sexual activity. The sad fact was that in those data where they did have time-diary on sex, sex was a very rare activity. These were either monks, or nuns, or liars. I don’t know which. For that reason I said, “Let’s think of something bigger, which is sleep.” Which is the most common activity in terms of time spent that humans engage in.

In 1989, Hamermesh 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.

HAMERMESH: That was the crucial question. We found that they slept less, those who had better earnings opportunities.

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.

HAMERMESH: Indeed, when this research was first written up in 1989, the headline was “Sleep, Why Bother? It Costs Too Much.” 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.

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

HAMERMESH: 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. If I don’t sleep enough, it’s going to wind up hurting my productivity and my eventual earnings ability. 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.

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

That, again, is Matthew Gibson.

GIBSON: I believe it affects my performance. Also, I’m frankly a much better human when I get eight hours than when I get six.

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

GIBSON: I have one of these goofy apps on the iPhone that plays rain sounds. I run that all night. I end up sharing rooms with other economists at conferences sometimes and there’s always this awkward moment when I say, “Do you care if I play the iPhone rain sound tonight?” Most people would be reluctant to reveal their true feelings. I usually get a funny look followed by assent.

Gibson wanted to build off the Hamermesh 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 Shrader, another Ph.D. candidate at U.C. San Diego. In a perfect world, they decided, they would run a giant sleep experiment.

GIBSON: 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. 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.

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

GIBSON: 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 U.S. in 1883. Once the railroads got on this bandwagon, the federal government rather quickly followed. Before that, each local area kept its own idiosyncratic time. If you journeyed any appreciable distance and showed up in the town’s square, it might have behooved you to look at the clock outside the bank or the clock on the town hall to say, “What time is it for people in this town?”

Today, there are four time zones in the continental U.S. – 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.

GIBSON: Amarillo is the birthplace of my illustrious co-author Jeff Shrader.

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.

Tommy BATTLE: Usually, sunset is around 7:30 right now.

By the height of summer, sunset would be close to eight 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, Marsha Shrader.

Marsha SHRADER: I am the mother of Jeffrey Shrader, who is studying economics at the moment.

Shrader, you’ll remember, is Matthew Gibson’s co-author.

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

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?

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

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

GIBSON: If we 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 nice straight line with earlier bedtime for people at the more eastern location.

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

BATTLE: I’m an early-to-bed person. I’m 9:30 to 10:00, I’m in bed.

And Marsha Shrader, in Amarillo.

SHRADER: 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.

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.

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

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

GIBSON: If I dose you, the person in Huntsville, with a one-hour-earlier sunset time, how much more do you sleep? The answer is, something like an hour per week. 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.

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

GIBSON: 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?

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

GIBSON: 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 percent.

Four and a half percent — 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 Shrader 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.” Sixteen percent, really?

HAMERMESH: That seems huge to me.

That’s Dan Hamermesh again. He read an early copy of the paper.

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

GIBSON: 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.

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 Shrader in Amarillo what she made of her son’s findings.

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

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.”

GIBSON: Workers don’t have an incentive to move in response to those sunset doses.

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.

GIBSON: 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 7-21 days, 1-3 weeks. They found very large effects on task performance, on these lab type of tasks.

DINGES: Right away you see the cognitive effects.

David Dinges is a professor of psychology and psychiatry at the University of Pennsylvania.

DINGES: 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 full alert.

Dinges and his colleagues have conducted several important sleep trials over the years:

DINGES: If went from seven or eight hours a night down to six or five, the more we got this cumulative rate of build-up 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. There was a dose-response function. The less sleep you got chronically, the more rapidly you deteriorated. The two things you see first are you cannot sustain attention for very long. You try to compensate by then becoming impulsive. What happens with, paradoxically with chronic sleep restriction is people will be slow to respond, or lapse. Then they’ll be overly impulsive and maybe talk or interact a lot, and then suddenly be out of it again. 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.

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. Matthew Gibson again.

GIBSON: One reason 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.

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.

Jens BONKE: You could call it a premium for getting up early in the morning.

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

Spencer ROTHFUSS: 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.

ALLEN: My name is Mark Allen. I’m calling from North Queensland in Australia. What do I wear? Butt-naked is the American way of saying it.

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

HILL: Hi, my name is Adam Hill. Eating dinner late actually improves my sleep quality.

BATTLE: I’m Tommy Battle, mayor of the city of Huntsville, Alabama. I’ve 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.

Rebecca MILLER: This is Rebecca Miller, and I live in Pleasant Grove, Utah. In high school or college I would work the graveyard shift. I would sleep in a closet sometimes and wrap like a shirt around my head so that I would convince my body that I was sleeping at night when really it was the day time.

Kecia WALDSCHMIDT: My name is Kecia Waldschmidt. 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.

*      *      *

CAMILLE (Singing): Good morning. Hello. It’s nice to see you, daddy.

Are you a morning person?

CAMILLE (Singing): Good morning. Good morning. Good morning.

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

Christopher WERTH: What do you want to do?

CAMILLE: Daddy, I want to wake up.

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

CAMILLE: Yeah!

Dad wouldn’t mind getting up a bit later.

WERTH: Big yawn.

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.

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

That’s Jens Bonke. He’s an economist and a senior researcher at the Rockwool 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.

BONKE: For that reason, I said, “If the morning-type people are favored, they might be more productive. They might earn more than evening-type people.”

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

BONKE: That was what I decided to investigate. My assumption was that there might be a relationship between when you sleep and how much you earn.

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. Bonke 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.

BONKE: We have a lot of information on every Dane in this country here.

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.

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

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

BONKE: There was a significant differential in the sense that morning-type people earn 4 or 5 percent more than evening-type people.

Four to five percent more for the early risers! And that’s controlling for family background, education level, and so on. Bonke 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). That doesn’t seem fair, does it – to get punished in the workforce because of your night-owl genes? So what should be done? Bonke argues that more flexibility in the workplace – even in the very pace of the day – would be a big help. 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.

BONKE: You couldn’t do shopping most places after 2:00 p.m. on Saturdays until Monday morning. At most workplaces, you had to be there from 8 o’clock in the morning to 4 o’clock in the afternoon.

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 Bonke 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 percent more than night owls. He compared this result with the same data from ten years ago.

BONKE: There, I could see that the premium for getting up early has decreased considerably over this period.

A decade ago, early birds earned 10 to 12 percent 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.

BONKE: The Danish labor market — probably most labor markets — [allows] 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 possible for men.

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 U.S., 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. This is Chennai, the sixth-largest city in India.

Heather SCHOFIELD: Which actually means it’s huge. It’s bigger than Chicago or L.A. So it’s a lot of people packed into a fairly small space.

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

SCHOFIELD: Everybody honks a lot because it’s a way of telling people where you are on the road and that you’re coming. It’s constant auto horns all the time.

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

SCHOFIELD: There will be three or four other people in this eight-by-ten room trying to sleep at night. Any time 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. If that weren’t enough to make it really hard to sleep, there are probably mosquitos there as well. It’s a very tropical climate. They’re buzzing around your head, biting you, making you itchy. It’s an incredibly difficult environment to sleep in.

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.

SCHOFIELD: These other things like sleep, which somehow haven’t 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 immediate that it actually has these productivity effects — which is exactly why we’re trying to study it and really understand what those implication are.

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

SCHOFIELD: You know, you get a picture that looks a little fuzzy.

And you have to decipher it and type out AB52 or RGB7Y, whatever it is.

SCHOFIELD: The reason they use them is because it’s hard for computers to do that. They actually need a human to generate the correct answer so that they can check your answer when you enter it as well.

The people who double-check your captcha entry earn two to four dollars per day. Schofield wants to learn if improving their sleep will help them earn more money.

SCHOFIELD: Basically, we’ll conduct a lottery and half the people in the study will be given things to help them sleep better at night. 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 mosquitos away. They’ll also get an eyeshade and ear-plugs 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 where it’s cool and comfortable and take 20 or 30 minutes just to rest because there’s actually pretty good evidence from work here in the U.S. and in other developed countries that short naps of 20 or 30 minutes can improve your cognitive performance and your ability to focus.

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

SCHOFIELD: We can see everything that you do in doing your work. How many data points are you entering? When are you doing them? How quickly are you doing them? Hw accurate are you? Work is compensated according to how much and how well you do. 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.

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.

SCHOFIELD: 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 as productive as possible in the labor force. If we can help improve their sleep, our hypothesis is that it will improve the ability to both work longer, work harder and work better. Improve their performance on the job in quite a variety of different ways. More broadly, to improve the choices that they’re able to make.

Doing this research has made Schofield more aware of her own sleep deficits — she’s constantly flying back and forth between India and the U.S. — and how hard it can be to get enough sleep.

SCHOFIELD: It’s this constant battle. I know — from all the stuff that 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 much better on. But it’s a constant tension. It’s one of those things where there are a lot of other constraints on your time. I’m very aware of it, but it doesn’t make it easy to change. But I have also realized that 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.

or example: she bought a pair of high-end ear plugs and learned the best technique for putting them in.

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

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 turned to Dan Pardi.

Dan PARDI: I’m the CEO of a company called Dan’s Plan.

Dan’s Plan is a sort of health consultancy in northern California. Pardi 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.

PARDI: You want to wake refreshed and feel alert all day every day. “Cool. How do I do that?”

He recommends that you start with a personal sleep experiment.

PARDI: 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. The body wakes itself up and not by something else. How much time is that? See how much time you need on average. Write it down. Having that number, that time in your mind clearly established is a very good thing.

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.

PARDI: If you’re used to going to bed at midnight and getting up at 8:00, your body is primed to get really robust REM sleep around 4:00, 5:00, 6:00 in the morning. And so, when you shift that, then you’re not going to get as good of sleep as you would like.

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

PARDI: 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. Part of the brain is keeping track of what time of day it is, to say, “It’s this time of day. Do this type of activity.” All of the body runs on these clocks. It knows what to do when. Two hundred years ago, 90% of the United States was agrarian. We were outside all day tilling the fields, getting a lot of sun exposure. As the sun went down, the tone and the intensity of light would change, and that stimulates some darkness hormones, which facilitate the occurrence of sleepiness, which could then ushers in sleep. Now we spend 90% of our time indoors. That’s a huge shift. The intensity of light indoors is surprisingly different than the intensity of light outdoors.

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

PARDI: Now, we can artificially manipulate our light environment to evening through room light and high definition televisions and screens . That gives a daytime signal to the brain at night. What ends up happening is those rhythms become desynchronized. We’re creating a state of minor, perpetual jet lag by the way that we live, by having mistimed lighting.

So what you want to do, Pardi says, is re-synch 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.

PARDI: What that means is that I can see, but I’m not telling my brain that it’s day. When blue light is entering in the eye, it will suppress the release of melatonin. 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. What it does is it tells the body that it’s night. The big benefit of that is that I wake up much more refreshed the next day. I am ready to go and I function pretty well all day long.

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:

CAMILLE (Singing): Good morning. Good morning.

Or any of the other sleep-interrupters that all of us encounter:

Maren MONTALBANO: My husband’s not in town, and I never sleep well when he’s not here.

But it’s nice to see that people like Dan Pardi — 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 we control, affect those outcomes. Yeah, there are a lot of things beyond your control. But in terms of what you eat and drink; 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. After hearing from all these sleep experts the past two episodes, I’m convinced we’d all be better off it 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 11:00, 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 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, 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. 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.

Hey, sorry to wake you but, on the next Freakonomics Radio, we put our FREAK-Quently Asked Questions to Aziz Ansari, the comedian, actor, and now author. You can also reach us on Twitter, Facebook, and elsewhere. All right, I’ll shut up now. Sweet dreams.