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Steven LEVITT: My guest today, Leidy Klotz, is an engineering professor at the University of Virginia who works at the intersection of engineering and behavioral economics. Who even knew those two fields intersected? 

Welcome to People I (Mostly) Admire, with Steve Levitt.

LEVITT: Leidy summarizes his research ideas in a new book, it’s called Subtract: The Untapped Science of Less. Now, being totally honest, when I first saw Leidy’s book, I dismissed it as shlock, one of the hundreds of mediocre pop-science books published every year. But my friend Sendhil Mullainathan, who you might remember from two previous episodes of this podcast, said “No, Leidy’s book is different. There’s something really fundamental there.” And Sendhil’s right about everything. So I gave Subtract a second chance and I realized, yes, there actually is something here. With my newfound appreciation for what he’s doing, I’m excited to talk to Leidy for the first time now. 

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LEVITT: You’ve written a book called Subtract and you’ve done a ton of academic research on the topic, like most good ideas, it seems like there’s an extremely simple insight at the heart of your argument. What is that? 

Leidy KLOTZ: When we try to improve things, our first thought is what can we add to make this better? And as a result, we overlook subtraction systematically.

LEVITT: I think there’s an even simpler statement, which is that there’s a human bias against subtraction. Behavioral economists have been working on biases for 40 or 50 years

KLOTZ: Right.

LEVITT: And I think it puts it squarely in the idea of “Here’s something that doesn’t happen as much as it should.” And that’s the nature of what bias is. So, do you like that description or you do not like the description? 

KLOTZ: I like it. One quibble would be with what we don’t want to just have this considered alongside the laundry list of biases that are out there. Some of them less fundamental than others, because we think this is a pretty fundamental one. 

LEVITT: But there are some pretty good biases on that list. Don’t you think?

KLOTZ: Oh yeah. Yeah. No, there’s ton of great biases.

LEVITT: Everything from hyperbolic discounting to defaults to loss aversion. So I don’t know — if you don’t want to be on that list, I’m not sure what list you do want to be on. 

KLOTZ: Any of the Tversky and Kahneman biases, we will be on that list, happily.

LEVITT: Okay. Let’s at least stick with that term for now, which is that I’m going to summarize your idea as being there is a human bias against subtraction. And I want to just pause, because good ideas are extremely rare and it’s too easy for humans to say, “Oh, that’s totally obvious.” Or, “That’s not true.” And I have to admit that my own first reaction to your idea and to your book was negative. It was only when I slowed down and I chewed on that idea a little bit that I realized two things. First, the idea really was new to me. And second, I suspect you’re right, that there actually is an innate bias against subtraction and it’s not easy to uncover something that is both new and correct. So let’s just start with the academic studies because I suspect that people have no idea what we’re talking about

KLOTZ: Okay.

LEVITT: Because subtracting is so abstract. But how did you begin to convince yourself that this was important? 

KLOTZ: The first study was just really simple Legos that we had out in front of passers-by on the university campus. And so we said, “Okay, here’s a Lego structure. How would you make this thing better?” And it was totally open-ended. And out of 60 participants, I think only one person took Legos away from that. The basic idea we’re testing here is when you have a situation, whether it’s Legos or a travel itinerary or the thoughts that are in your head, how do you try to make it better? And the Legos, that example shows that 59 out of 60 times people added to try to make it better.

LEVITT: But you didn’t build an arbitrary structure. I suspect you built a structure with, one beautiful subtraction would turn it from a piece of junk into the Taj Mahal

KLOTZ: Yeah.

LEVITT: But nobody could see that. That must have been the gist I’m guessing of what you were doing. 

KLOTZ: We started with arbitrary structures and then we moved into things that would be better if you subtracted. The challenge people had was, put a masonry block on top of this Lego platform. It was a wobbly platform, like a table with only one leg. If you just threw a masonry block on top of the structure that we gave them, the structure would collapse and you wouldn’t satisfy the parameters. And so you could create the structure that we wanted by either adding eight blocks or removing one block and we charged people for block additions. And most people would add filling out all three legs of the table. Whereas you could just take one of the legs away, move the platform down one level and it would be totally stable. 

LEVITT: You charged them to add, you charged them nothing to take away. And yet almost everybody added when the simplest solution was right in front of them, just take away. 

KLOTZ: Yeah.

LEVITT: How about travel itineraries? What were you doing there? 

KLOTZ: You’re imagining your own trip to Washington D.C. And so we created this obnoxious travel itinerary, like seven activities from 10 to 3, and then seven more activities from 4 till 10 at night. And then people could remove things from their itinerary or they could add more things and people tended to add even more stuff to that already jam-packed, impossible itinerary.

LEVITT: Sometimes the question in these experiments is whether the costs and the benefits end up being real. Did you actually make the people go and do that day of sightseeing in Washington, D.C. to punish them for their inability to subtract? 

KLOTZ: No, we should have. There were nine preliminary studies that we did that just basically showed people adding in all these different ways. The range was probably 80 percent adding, 20 percent thinking to take away. It was a big difference. And the core experiments were things that showed people weren’t even thinking of subtracting as an option.

LEVITT: So you do a whole series of studies in a bunch of different settings and you see over and over that people don’t seem to want to subtract, they always want to add. So now you’re faced with the challenge, which is why? And so you designed some more studies. So, give me an example of an experiment where you can figure out whether people consider subtraction and then ignore it, or it just doesn’t even cross their mind because they’re so focused on addition. 

KLOTZ: I’m an engineer by training and I’ve worked in behavioral science for the last 13 years but I was working with three other behavioral scientists, Andy Hills, Ben Converse, and Gabe Adams who are really magnificent at designing these experiments. And Andy, who’s a professor at the University of Mississippi, came up with this grid design. So you’ve got this large grid of 120 spaces broken into four quadrants. There’s a line down the middle, vertically, and a line down the middle, horizontally. It’s like a checkerboard with some of the spaces already filled in and we would fill them in in a way that was a pattern and we would leave extraneous marks in one of the quadrants. You’ve got to make it symmetrical from left to right and from top to bottom. One example, we drew something that looked like a diamond that was centered in the grid. So that’s symmetrical because it looks the same left to right. And top to bottom. And then in addition to that diamond, you might put three extraneous grid marks in the upper right corner. So now you’ve got one quadrant of that master grid that is different than the other three and we’ve asked the participants to make it symmetrical using the fewest clicks possible. So one way to do that is to add to all three quadrants —

LEVITT: So, does that cost you nine clicks? Because you’ve got to add three extra spots in three quadrants. 

KLOTZ: Exactly. And then the other way to do it is to subtract from one quadrant, which only costs you three clicks. 

LEVITT: And this is so totally obvious

KLOTZ: Yeah.

LEVITT:  That I’m sure everybody just did the subtraction of three, right? 

KLOTZ: No. I mean, I think I would fall for it the first time. And even now when I open presentations with this, “Leidy Klotz talking about subtract and his new research, why people don’t subtract” and still people overlook it.

LEVITT: And a lot of people — most people faced with that ex-post incredibly obvious chance to subtract, do addition. 

KLOTZ: Right. From a purely rational standpoint here, it should be zero. 


KLOTZ: It shouldn’t be 50-50. It should be zero. So anything above zero is people missing the correct answer.

LEVITT: And so if you cue them, if you in your instructions say, “Hey, don’t forget, subtraction is an option,” Then I assume that tons of people must subtract.

KLOTZ: So, we cued them not just by saying, “Hey, you can subtract,” but by saying “you can add or subtract.” And what was interesting there is it increased the rates of subtraction, which, then a skeptic might say, “Of course. A reminder is gonna increase the rates of everything.” But it didn’t increase the rates of adding. And so what that shows is that the adding reminder is redundant with what people are already thinking. And the subtracting reminder is bringing a new idea to mind, which is what our core finding turned out to be that we systematically overlook these subtractive options.

LEVITT: And my hunch is that people get better at this over time. So, if you give them a grid where it is completely and totally obvious that they should subtract, my hunch is that when you give them other grids in the future that are less obvious, they’ll be more likely to subtract in that setting, as well, then in a case where they’ve never been encouraged to subtract before. 

KLOTZ: That’s true. One of the other things that we did was see if we gave people repetitions of the grids, would they, after stumbling upon a subtraction, then be more likely to recognize it as the correct thing. And so if you said, “Okay, solve this grid three or four times in different ways,” and then on the third option, they’re like, “Oh, I could remove these blocks.” And then at the end, you said, “What’s the right answer?” Of course, they recognize that subtracting the blocks was the correct answer. So yeah, the repetition helped. And all these biases, there’s helpful history to them, right? They’ve proven helpful in the past and they’re just our default settings. One indication that something is a bias is if you’re relying even more on your default mental settings, you are even more likely to succumb to this bias. So we gave people the grid studies, for example, with a number line scrolling across the bottom of the screen. And every time a five came across, they had to press an “F” on the keyboard. So this is simulating, “Hey, you just got other stuff to think about.” And when people were under that additional cognitive load, they were even less likely to find the subtractive answers. So they’re more likely to go with this adding default and less likely to do the little extra thinking required to take away.

LEVITT: Yeah, that’s really interesting. That’s like the cleverness, which when you say it, people won’t fully get how hard it is ahead of time to think up those kinds of experiments. But that’s really neat because somehow subtraction — it’s hard for people. It’s not right there. And so when you distract them by making them do unpleasant tasks, like look for fives, it slows them down.

LEVITT: Now I would say in general, I’m pretty skeptical of lab experiments. I think real-world examples are really critical to convincing me that this idea is important. So how about we take turns giving some real-world examples, which will be messier and I’ll compliment or critique your example, and you can do the same to mine. 

KLOTZ: Yeah. So Strider bikes. If you’re fortunate enough to have a two-year-old in your life, these are these new little kid bikes. And they don’t have pedals on them. And as soon as your kid can walk, they can walk on top of this bike. And then after about an hour of walking, straddling this bike, they figure out that they can push their feet like a Flintstone’s vehicle. And maybe another hour after that, they’re literally balancing on top of this bike. They can reach speeds as fast as a sprinting father. The insight here is by this guy Ryan McFarland, who founded this company Strider bikes, and it’s just — he took the pedals away. I tell the story in the book, but he was basically sitting there thinking about how to lighten the drive train. And then he’s like, “What if I just take the whole thing away?” And that’s what led to this balanced-bike insight, which has given mobility to all these two-year-olds. Plus, the beautiful thing about it is then once the kids go to ride a pedal bike, they don’t need training wheels. They already know how to balance and they just need to get the leg power to pedal. Inarguably, great improvement to our world and the insight there was subtraction. People will quibble with this example, but the point is that for a long time there was all this innovation in the kid’s bike market, whether it’s training wheels, little cabooses on the back of a bike, fatter tires, fatter tubes, and nobody thought to take away the pedals to make this bike that was better for two and three-year-olds.

LEVITT: Yeah I don’t think the quibbles against that one are fair because


LEVITT: Look, training wheels just are not very good practice for a real thing. And what I like about it is it took a long time, but as soon as somebody did it, it was totally obvious. Let me give you an example I have, which is in a totally different space. 

KLOTZ: Okay. 

LEVITT: So after Stephen Dubner and I wrote Freakonomics, I was approached by a lecture agency and they told me that there’s a whole industry of speakers who go around and get paid to give talks at conventions and company events. If you’re good at it, people pay you outrageous amounts of money to give speeches. Okay, but the key really is you need to be good at it otherwise no one will hire you. And this lecture agency wasn’t so sure that I’d be very good at it. So they hired a public-speaking coach who would work with me to try to improve my speaking. I, somewhat reluctantly, agreed to meet with this person once, I wouldn’t commit to anything more. I didn’t really want to be a speaker. What I wanted to be was an academic who every once in a while went and gave a talk. So the speaking coach, it turns out, lives in Los Angeles and is being flown into Chicago and he says to me, “Basically you do everything wrong. If we work together for two to three hours per week for a year, I might be able to make you an average business speaker.” Before I could even say, “No, thanks. I’m just going to be an academic.” He kept on talking and he said, “But the weird thing is, audiences like you. So I’m going to suggest a different path. I’m going to give you a few pieces of advice and I’m just going to let you be.” So his first piece of advice was, “You should never, ever wear a necktie. Audiences seem to relate to your authenticity and when you put on a necktie that just completely gets destroyed.” And his second piece of advice was, “Never stand behind a podium. In order for you to be effective, you need to seem vulnerable. And the podium is your enemy because it’s an interloper between you and the audience.” So what’s interesting to me is all the levels at which subtraction were operating here. Because first he could have billed the lecture agency for hundreds of hours of billable time, by trying to craft me into something that I wasn’t, but he decided not to. But second, both of those first two pieces of advice were subtraction. No necktie, no podium. So what do you think of that example?

KLOTZ: I think it’s an amazing example. Like, this speaker coach obviously knew all the additive ways to make you a better speaker. And he filtered through those in his head, considered them, discarded them, and not only didn’t pile those on top of you but also picked some subtractive suggestions. Plus it’s just nice not to have to wear a necktie.

LEVITT: That’s true. And the other thing that’s really subtle is that no podium means no notes because you can’t really stand in front of an audience holding notes if you don’t have a podium to put them on. And that’s the biggest subtraction of all because once I realized that I didn’t have the crutch of notes, I had to do some addition, which was to do a lot more prep. But it made me much more effective to actually speak in an authentic way without notes than the old me who was always trying to read what I was doing. 

KLOTZ: It shows the extra work to subtract in this case, because what you just mentioned there is not, hey, show up without notes, Steve. It’s, show up without notes because you know the material even better. So you’ve actually had to do more to take away. 

LEVITT: It just got me thinking about whether maybe authenticity is the ultimate act of subtraction or expression of subtraction — that all of us spend all our time trying to be and do what we think other people want us to be and do. And maybe somehow in some philosophical sense, if we buy into your idea of subtraction, it would lead us towards some kind of authenticity. But maybe I’m just crazy. 

KLOTZ: No, I like that. Don’t call it my idea of subtraction though. I think it’s — I’m agnostic. People go around, “Oh, Leidy says we should always subtract.” I just don’t want us to overlook the option. But I love the authenticity piece and it certainly seems like the stuff that is inauthentic, you can strip away. That’s something that is prime for subtraction. 

LEVITT: But you need to think about it. Society just puts a lot of pressure on us to be normal. I’m socially awkward enough that I don’t even notice a lot of societal pressure. And it’s been really helpful to me in maintaining, I think, the only thing that I have that’s any good at all, which is my own authentic way of looking at the world.

LEVITT: Let me give you another example from my university center, the R.I.S.C. Center, R-I-S-C, that I run, where we try to do social good. 

KLOTZ: Right. 

LEVITT: And what’s interesting is I would say the majority of our projects end up being subtractive. So we are trying to rethink the criminal justice system. And one of the technologies that people use is called an ankle monitor. It’s an alternative to locking someone up. And I think, you know what I’m talking about —.


LEVITT: It’s a big, bulky piece of machinery and it provides a way of monitoring a person’s movements, but all else equal, people don’t really want their movements monitored. So companies build these big heavy devices and they’re locked and they’re uncomfortable. And because they’re so big, they’re visible to employers, and the companies compete to have the ankle monitor that’s the toughest one to cut through. But here’s the thing, even the hardest ankle monitors to beat can be cut through in 10 or 15 minutes. Okay? After all of this technology and this work, anybody with a, with a —.

KLOTZ: Bolt cutters. 

LEVITT: Bolt cutters, yeah, exactly. So essentially the fact is if somebody wants this ankle monitor off, they can get it off, which we think means that it’s a perfect case for subtraction because the simple reality is that people can cut through any ankle monitor, but very few people actually are doing that in practice. So why? Well, because if you do it, they come and get you and they lock you up. There’s not really a big desire of people to take these off because we’ve set the incentives such that you don’t want to take them off, which means that there’s a much simpler subtractive solution, which is a little device like an Apple watch. And it’s not bulky. It’s not degrading. It’s not like a shackle. It won’t interfere with your life, your jobs. And it also potentially opens up all sorts of possibilities, changes to the dynamic where it can move from a shackle with some primitive stigmatizing monstrosity, to rather enabling with a technology that could provide social services or let the person wearing it reach out to a parole officer if they’re in trouble to try to get problems solved. So, anyway, I don’t know. What do you think of that as an example of subtractive thinking? 

KLOTZ: Oh, it’s beautiful. And it ties into my engineering background. I mean, I just see parallels. Can I give you one engineering one?

LEVITT: Yeah, please. Yeah. 

KLOTZ: So there’s this really cool engineering idea and somebody should write a book about this inventor, too, her name’s Anna Keichline she was the first woman architect in Pennsylvania. And then she was a volunteer spy in World War I. But in between being this Renaissance woman, she was also a serial inventor. And one of the things that she invented that has shaped our modern society is the hollow building block. These are the building blocks made out of concrete. So she invented it in like 1920 — before Keichline, building blocks were solid. But these hollowed-out blocks, you can fire them more quickly. They’re easier to move around because they’re lighter. They use less material — a big portion of our CO2 emissions come from concrete. So this uses less concrete and these hollow blocks actually provide better insulation in buildings because instead of this straight conductive unit of material, you’ve got an air barrier in the middle. So it’s just inarguably better. 

You’re listening to People I (Mostly) Admire with Steve Levitt and his conversation with Leidy Klotz. After this break, they’ll return to talk about what to do about our bias against subtraction.

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Morgan LEVEY: So Steve, in our episode with David Epstein, you propose that our listeners try an experiment. 

LEVITT: It would be interesting if a listener who had passed up on an opportunity at a high prestige academic institution did a little randomized experiment. If they included that information on some job applications and not on others to see whether it affects the likelihood of getting a first interview. I’d be really interested to see how that turned out.

LEVEY: Well, a listener named Adam K. tried this experiment. He was accepted into a master’s econometrics program at the London School of Economics for this year, but he decided not to attend. He included this fact on his resume for some, not all of his job applications and found that he actually got more responses using the resumes that listed the program on it. So what do you think of Adam’s experiment?

LEVITT: I love everything about it. I love that Adam went out and actually created this random or quasi random variation. I love the fact that he took the time to carefully keep track of the results, but what I love more than anything is that he saw these results. He saw that he was getting more callbacks when he included the information about the program. But then when he actually did the interviews, he realized it was because the recruiters actually just made a mistake. Most of the recruiters misread his resume and thought that he’d actually done the program. So I love the fact that he actually was a careful analyst of what he saw and actually learned from it. So he didn’t draw the wrong conclusions. I mean, this is social science at it’s best is what I’d say. Adam, you went out and you actually created knowledge and it was interesting and it was easy and it’ll make your life a little better and maybe it will make other people’s life a little better. I wish there were more people like Adam in this world.

LEVEY: I think we should underline that people shouldn’t lie on their resume, but if a recruiter does misread something, then that’s on them.

LEVITT: Another nice thing about Adam — so he’s not only a good scholar, but he at least professes to be honest because he said that with each of the recruiters who mistakenly thought that he attended the program, he was careful to correct them. So look, Adam wins and not only for smarts, but also for honesty, too.

LEVEY: Well, Adam, thanks so much for trying this experiment and sharing your results with us. If you have a question for us or want to respond to something Steve asks on a show, please write in. Our email address is Steve and I both read every email that gets sent in. We look forward to reading yours.

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LEVITT: I expected there would be a lot more conflict in our conversation than there has been so far because, while I love the core idea that there’s a bias towards subtraction, and I love some of his examples, like the Strider bike, I also hate many of the other examples in his book. But I give Leidy credit for good taste in this discussion because so far he’s managed to only throw out the examples that are hard to disagree with. Let’s see if that continues or whether the conflict ramps up in the second half. 

LEVITT: Why do you think the bias against subtraction exists? You think it’s an evolutionary thing or comes from somewhere else?

KLOTZ: I think it’s a combination of a lot of things. We look at evolutionary reasons for this, cultural reasons for this, and economic slash social-system reasons that this might be happening and all of these forces work together. So there’s not going to be a single reason, but evolution, it’s easy to think about, okay, we’ve acquired food. That’s helped us pass down our genes, generation to generation. Also, an evolutionary force is just this desire to display competence. And then the classic example, there is these bowerbirds building ceremonial nests. The male birds build the nest, the female birds go around and choose which male to mate with based on how much they like the nests. And then, the female bowerbird goes and builds an actual nest to raise the kids. So the whole purpose of the nest that the male built is just to show that the male is effective at interacting with the world. If we think about this culturally, for a really long time it’s just made sense to add. If you don’t have a city, it helps to start building roads and infrastructure. If you don’t have a society, it helps to start adding writing and adding laws. We’ve all evolved from civilizations that have developed that way. And so this kind of historic adding could spill over into our thinking now. And the other way that it spills over — it’s less in a evolutionary way — it’s more just, we’re surrounded by this stuff all the time. So if you’re just walking through your world, Steve, you see a reminder of the building that was built. You see a reminder of the legislation that was passed. And we don’t see reminders of the stuff that’s been subtracted to make things better. And then the last one is just this idea of some of our economic incentives pushing us towards more. Gross domestic product, for example — as that goes up that’s one measure of a country’s progress and that certainly pushes us to add because if you build something bad, like a prison, for example, that’s increasing gross domestic product. So that counted as a good thing. So there can be these perverse metrics that lead us to add too.


KLOTZ: The one in my book is actually — less lofty and it’s more just my own house. I’ve been interested in subtraction for a long time. So this was even before I wrote the book, I said, “Okay, we’re going to do a home renovation.” I’m teaching a class with engineering and architecture students and the theme was addition by subtraction. And I gave them all of this reading about subtractive minimalist, modern design. And I specifically challenged them to make the home better without adding any more square footage and by subtracting square footage, if possible. And of course, nobody came up with a design that subtracted square footage. 

LEVITT: Wait, why do you say “of course”? 

KLOTZ: I just — because we’re talking about subtraction and people overlook it and it’s hard. 

LEVITT: I know but you primed them — you made it clear you wanted — you must be not very persuasive if you can’t even get your students to believe that what you really want is what you’re saying. 

KLOTZ: I don’t know if I really wanted it. I think they were smarter than me because we ended up adding 900 square feet to our house. In this case, adding was just better. We needed more space and that was the right solution for us. But the economic force there was just the cost. The home’s being valued on square footage. And as we talked to our realtor, we’re like, “How can we increase the value of our house?” And she said, “Just increase the square footage.” So in that case, there was an economic incentive to add. What’s wrong with my logic there?

LEVITT: What’s wrong with your logic is a lack of authenticity. You shouldn’t ask your real estate agent what you want and do it because society says they’ll pay you for it. If you were truly authentic to what you needed and believed, then you could have had less space, but created something so magical that people would’ve loved it. That’s my critique of that one. 

KLOTZ: Okay.

LEVITT: It’s obviously somewhat tongue in cheek but I do think that’s an interesting case where you and your wife didn’t have the confidence to go and do what you wanted to do because you were afraid of how the market would react to it. And I think, in a subtle way, the message that I took away from your book is “Don’t let the fact that everybody else is additive trick you into being additive too.” 

KLOTZ: Yeah, the home example, I think we were authentic with that. This is what we needed. And I think the authentic piece there was like, okay, Leidy talked about subtraction, but he thoughtfully considered all of the options and decided that adding was better. 

LEVITT: Okay, good. So that is authentic —

KLOTZ: Yeah.

LEVITT: Because really you want — let’s just be clear because I’ve maybe been taking too strong a case — it’s not that you go through life preaching that subtraction is the answer to every problem, you’re going through life preaching that subtraction should be on the table. Don’t overlook it. Sometimes subtraction is good. Sometimes it isn’t and we miss out on opportunities to use it. And that’s what a bias is. It’s not that it’s always the right thing. It’s that it’s used too little relative to what would be optimal. 

KLOTZ: And back to your authenticity point. The untapped part is the longer we’ve been using this bias, the more untapped subtractions have piled up. 

LEVITT: So I want to throw out another reason why I think people have a bias against subtraction. And I think when you don’t understand how things work and let’s face it, the modern world is complicated, and almost no one understands how anything works. So when you don’t understand how things work, I think it’s risky to start subtracting. So you think some piece doesn’t matter —

KLOTZ: Right.

LEVITT: Or it’s making things worse, but then why is it in there? Presumably, someone in the past who maybe knew a lot more than you put it in there for a reason. And it’s just better not to mess with it. Now, I’m not saying that’s the right answer, but I think that’s a really strong force. And I think it’s a strong force now, but I think that was a strong force 5,000 years ago when there wasn’t really any progress. Your grandparents would tell you, “Don’t eat that plant.” And I don’t know why I’m not eating that plant, but grandma’s survived to the age of 60. So she must be pretty good at this. I’m not gonna eat that plant. And I tell my kids that. So do you think that has anything to do with why maybe we don’t do as much subtraction as we should? 

KLOTZ: Definitely. If you’re messing around with your engine of your car, the same basic thing. Who am I to take something out of this? Surely there’s a purpose. I think that’s a good way to approach the world is to think, “Okay, if this thing exists, we need to have more of a reason to take something away from it.”

LEVITT: I think another thing this brings up in my mind — a force against subtraction is that anytime you take something away, there’s usually somebody who is benefiting from that thing that will be taken away. And that group is often politically, highly motivated, highly vocal. Whereas the beneficiaries of the subtraction are often amorphous. They don’t even know who they will be, who will benefit from something. And so I think that politically makes it hard because there’s almost always someone who’s trying to fight any change that involves taking stuff away. 

KLOTZ: One of the examples I use in the book is San Francisco’s Embarcadero freeway. This was a double-decker freeway in front of the waterfront in the city and planners have been talking about removing it basically ever since it had been built. They put it to vote among the city of San Francisco. And it was like two to one, wanted to keep the freeway. But the earthquake hit in 1989 and it made the freeway unusable. So now the choice was, hey, do you want to rebuild this freeway? Or do you want to now go forward with this plan of removing the freeway and experiencing those benefits? And still, public sentiment was not to take it away. The planning commission forced it through. But then the mayor got voted out of office in part because of the role forcing this through and the planning commission all lost their jobs. I think that it’s really visible and tangible what you will be losing when you take something away. And it’s harder to imagine what the gains are going to be.

LEVITT: So one of the things you recommend is shorter to-do lists and lists of things you should stop doing. Could you talk about that a little bit? 

KLOTZ: This allows me to talk about my friend Ben, who was also a co-author on the paper. So he comes to me like two years into our research together and he says to me, “Hey, I’m putting our research into practice.” And he installed this bell in their office. They called it a “No Bell” which if you said, “No,” to something you could ring the bell. He said, “My department chair came to me and asked me to be on the committee. And I said, ‘I’m really overloaded. I can’t do the committee.’” And I said, “That’s great Ben, but you didn’t, in fact, subtract there. You just didn’t add to your already overcrowded schedule.” And so the idea of a stop-doing list is just as you’re writing your to-do lists, think about things that you can actually take away. And they have to be things that you were doing — you were planning on doing this thing. You’ve been doing this thing for a long time. And so Ben’s partner, also a psychology professor, not only did she do stop-doings, but she will put the reminder on her calendar of the stop-doing. We talked a while back about how less has a noticeability problem when you subtract something, the evidence isn’t there as a reminder that, hey, you subtracted and that’s why you’re happy. So she will like, “Okay, I’m not going to this meeting anymore — this biweekly, college meeting.” I’m going to skip it and just get information from my colleagues. But she will actually leave a mark on her calendar. It’s like this time brought to you by subtracting the redundant meeting. That’s the idea of a stop-doing. 

LEVITT: One of the things that economists do much better than other people is understand the trade-off between time and money, because I think —


LEVITT: For many people, myself, for sure, my scarcest resource is time. So there are often cases where I could pay someone else to do something that I don’t really want to do anyway. And that buys me time. Now that’s not exactly subtraction. But the spirit of it is there in that it’s a way of finding ways to do less, rather than do more. So a great example of this was that the Chicago Booth Business School built a new building 15 years ago. And they put a relatively small underground parking garage under it. And so they charged high prices because there weren’t very many spots. And I don’t know what the price was. Let’s just say it was a thousand dollars a month. And there was a young faculty member who, as we were sitting around lunch, said, “It’s ridiculous they’re charging a thousand dollars a month to park. So I parked my car for free over here instead.” And one of the senior faculty members, Kevin Murphy, amazing economist says, “So how long does it take you to walk back and forth?” Then he says, “15 minutes each way.” And Kevin says, “Okay well, I have an idea. I want you to start parking my car at that other parking lot. And I’ll pay you a thousand dollars a month because you’ve already told us that you’re willing to do it for a thousand dollars. And so I want you to park my car at that parking lot. And then you’ll bring it to me whenever I need it back and forth.” And the guy said, “Are you crazy? I would never do that for you.” And Kevin said, “Look, you’re doing it for yourself, what’s the difference whether you save a thousand dollars or you get an extra thousand dollars from me paying you to do it? It’s really the same problem. Just the fact you’re doing it for yourself is irrelevant.” 

KLOTZ: Yeah, I love that. And I think the point is not the specific subtraction. The point is: put the cues in place so that you don’t fail to think of it as an option when you’re making decisions. So if you want to subtract more, force yourself to think of stop-doings when you’re making your weekly to-do lists. But also, think through the other times in your life, when you make decisions and how can you now put in place a cue to remind yourself to subtract when you’re making that decision. 

LEVITT: The more I think about it, the more I realize I already use subtraction all the time in my life and research. The abortion and crime argument is essentially subtraction and the solution that we’re proposing to fix high school math, cutting away much of what we’ve historically taught, that’s also subtraction. The list just goes on and on. And it makes me wonder how much of my success is due to the fact that I, unlike most people, seem to naturally gravitate towards subtraction. Not many episodes of this podcast yield such a simple, clear lesson that you can apply to your own life. The next few times you’re faced with a problem, pause and ask yourself how might subtraction help me here, and let me know what the outcome is. I’m so curious to hear about both your successes and failures when it comes to subtraction. Thanks for listening and we’ll be back next week. 

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People I (Mostly) Admire is part of the Freakonomics Radio Network, which also includes Freakonomics Radio, No Stupid Questions, and Freakonomics M.D. This show is produced by Stitcher and Renbud Radio. Morgan Levey is our producer and Jasmin Klinger is our engineer. Our staff also includes Alison Craiglow, Greg Rippin, Joel Meyer, Tricia Bobeda, Emma Tyrrell, Lyric Bowditch, Jacob Clemente, and Stephen Dubner. Theme music composed by Luis Guerra. To listen ad-free, subscribe to Stitcher Premium. We can be reached at Thanks for listening.

LEVITT: Okay. Your turn to give an example. 

KLOTZ: Oof. Um —

LEVITT: What do you mean, “Oof”? You have — you have a hundred examples. 

KLOTZ: I wrote this whole book — I thought we were done with examples. I like yours better. 

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  • Leidy Klotz, professor of engineering at the University of Virginia.


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