Planet Money - Summer School 2: How taxes change behavior and the economy

Episode Date: July 16, 2025

We all know the government uses taxes to pay for things. But what about using taxes to control behavior? This week on Summer School, Professor Darrick Hamilton of The New School, helps us explore the true power of the tax code. Can taxes help lift people out of poverty? What about saving the planet?Get tickets to our August 18th live show and graduation ceremony at The Bell House, in Brooklyn. (Planet Money+ supporters get a 10 percent discount off their tickets. Listen to the July 8th bonus episode to get the discount code!)The series is hosted by Robert Smith and produced by Eric Mennel. Our project manager is Devin Mellor. This episode was edited by Planet Money Executive Producer Alex Goldmark and fact-checked by Emily Crawford and Sierra Juarez. Engineering by Robert Rodriguez.Always free at these links: Apple Podcasts, Spotify, the NPR app or anywhere you get podcasts.Find more Planet Money: Facebook / Instagram / TikTok / Our weekly Newsletter.Help support Planet Money and hear our bonus episodes by subscribing to Planet Money+ in Apple Podcasts or at plus.npr.org/planetmoney.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy

Hey everyone just a quick message before class gets started planet money summer school is having a live Graduation ceremony and party in New York City on August 18th. It's gonna be great So get your tickets now before the show sells out planet money plus supporters get a 10% discount and Get early access to summer school episodes all summer long Check out the show notes for a link to buy tickets and to subscribe to Planet Money Plus. This is Planet Money from NPR. Welcome back, class, to Planet Money Summer School, the only economics degree that comes with UV protection for the beach, SPF 50. This season we're talking about political economy, which is a fancy

way of saying the role that the government has in our economy. And if you've been paying attention these days, you might have noticed that the government is all up in every part of our business. Today is class number two, taxing our way to a brighter tomorrow. I'm Robert Smith. One big reason to pay attention to what the government is doing is because they are doing it with our money. We ask more of our government and then they ask more of us through our taxes. At the very beginning of our country, Congress was desperate for money.

They levied taxes on imported goods, yes, a tariff as a tax, on things like whiskey, state's tax property. The first income taxes came to pay for the Civil War. Corporate taxes and sales taxes appeared in the early 1900s. The main thing taxes do is raise money. We all know this, right? Fund the military, insurance programs like Medicare and Medicaid, roads, bridges, all the stuff.

That part is pretty straightforward. The more money you raise in taxes, the more you can spend without borrowing a ton of extra money. Today in class, we wanted to zero in on a different way to think about taxes as a tool to shape the economy. Taxes can be used to redistribute income

to those who need it the most. Taxes can stimulate or slow economic growth. Taxes can be used to influence our habits and maybe even save the planet. With great taxing power comes great responsibility. That's why some of us love to talk about taxes. Well, as a person, I probably don't love taxes, but as an econ professor, absolutely. It is our biggest fiscal tool. Hey, before you jump in, you have to introduce yourself to the class. Oh, man. I quit. I'm out. So my name is Derek Hamilton. I'm a university professor and a Henry

Cohen professor of economics and urban policy at the New School. And I run an institute on race, power, and political economy also at the New School, and I run an institute on race, power, and political economy also at the New School. So taxes, ultimate tool of government. How does it work? How does the tax code change our behavior? How does it change society? It certainly changes behaviors.

It can incentivize various things. For example, if we offer a tax rebate or subsidy for people to green their house to convert from gas furnace to electric furnace, well, that's a change in behavior that presumably is good for the environment. Not presumably, it's actually good for the environment. And the government's also making choices when it has things like deductions, right? It seems like, oh, deductions, it's just something I do on my tax forms. But they have made specific ideas that we want to let you keep that money so you will

spend it for a specific purpose that we want you to spend it for. And famously in the United States of America, we have a deduction you can take for interest you pay on your home mortgage, which encourages people to own homes rather than rent them. Exactly right. I mean, we have a society that a lot of people not only live in their home, many Americans use their home as a mechanism to save, a mechanism to grow their wealth. And the tax code has incentivized that. And with every change in the tax code,

there are winners and losers. I always think of the different ways we tax forms of income. You know, a dollar isn't always a dollar. So a dollar made by a corporation, that may, you know, after accounting, get no taxes. A dollar made by selling something, capital gains gets maybe a low tax rate, but a dollar at my job, at least the most recent

dollar, gets taxed at a pretty high rate. Exactly. And you are describing the ways in which we structure behavior and frankly structure inequality by way of our tax code. So taxes reflect value. They reflect societal value. So if we tax wages at some rate, and then we tax, say, capital gains, which is a form of income that's generated from owning an asset.

Nat. Jensen Yeah, selling stocks, for instance. Nat. Jensen Selling stocks. Well, if we tax stocks at a different rate than we tax wages, that's reflective of values. Both of them generate revenue, but you could imagine that some people have greater access to wages versus some people have a greater wealth by way of reaping the rewards from, say, stocks, dividends from stocks. Well, over the course of today's class, we're going to hone in on some of the different

reasons and ways that the tax code can change behavior, both for the good and for the bad, and remake society, as you say, Derek, in the form of our own values. Here it is. After the break. Our first case study in this summer school class deals with taxes as a way to redistribute income. We often think of taxes as taking money out of our pockets, but for some people, it's the exact opposite. The tax code is a mechanism by which government can literally put money in the hands of people.

But it gets to choose which people. And it gets to choose which people. And the way it pulls off this trick makes all the difference, as we will learn in this classic Planet Money episode from 2013, hosted by Hannah Jaffe-Walt and Marianne McHugh. Tax Day is coming up. People love to complain about it, but not this woman. That is Lynn Matthews. She's a FedEx package handler and I met her at a pro bono tax center in Newark, New Jersey when she stopped in to get help filing her while she waited. And that's because for Matthews, tax time is bonus time.

For people like her, that bonus can be a big one. It can be more than $5,000. Often it's more than you paid in taxes for the entire year. Lynn Matthews is one of nearly 30 million people who receive this bonus. It doesn't sound exciting when you see it on the tax form. It's got a very technical kind of boring sounding name. It's the earned income tax credit. But Lynn Matthews doesn't find it boring at all. Our income credit, I'm so happy. I'm happy, yay!

The Earned Income Tax Credit is one of the biggest cash transfers we have in this country. More than $60 billion last year handed from wealthier Americans to poorer Americans. You'd think there'd be a lot of discussion about this, right? Right. And yet the surprising thing is almost everyone who looks at the Earned Income Tax Credit, the EITC, pretty much likes it, right? That's exactly right. It's been expanded by every president right and left since the 1970s. I'm talking Reagan, Clinton, both Bushes and Obama. As I was reporting the story, I talked to more than half a dozen economists left and right, and pretty much

all of them said that the Earned Income Tax Credit does exactly what it was designed to do. The architects of the EITC wanted to help poor people and at the same time, encourage them to work. And by God, they did. It worked. You know, the rocket was launched and it hit the moon. This is Richard Burkhouser of Cornell University and he told me that you do not see that kind of success very often when it comes to programs for the poor. I'm not exaggerating when I'm telling you, look, I've been doing public policy since

the 1970s and there's not a hell of a lot of these programs where you can see the tremendous change in the behavior of people in exactly the way that all of us hoped it would happen. So Marion, can you just lay out how it works? Okay, so very simply, the US government says, if you work but you're still poor, we're going to give you a bonus. And if you have kids, it's gonna be a big bonus, a big chunk of money. It could be more than a third of what you made all year. And it comes in one big lump sum.

When I was at the tax center in Newark, I met this woman named Mirian Ochoa, and she says she still remembers the first time that she got it. I'm saying, are you serious? This is for me? It was about three thousand dollars and that's after making only about nine thousand the whole year working part-time at a bank. And living on nine thousand dollars that is really hard. Ochoa had to seriously save every penny of her money. She told me that on her long commute to work she remembers going past this one McDonald's every day and smelling the french fries but

telling herself you have to say no because I have to pay my rent. Living on $9,000 is clearly very difficult and if you want to design a policy that's gonna help poor people giving them 3,000 more that seems like a pretty intuitive thing to do but the EITC the more you learn about it, the more counterintuitive it seems. So let's just walk through this. So imagine, you know, the way American policymakers have thought throughout history about helping poor people. You imagine the poorer someone is, the more help they need. So the more money you want to give them. So, for example, you get food stamps or you get subsidized housing, you get free government health insurance if you're poor. And if you start working and make enough money, you get

kicked off food stamps or you get kicked out of your housing, or you no longer have government health insurance because you no longer have need. And for most of us, we look at that and say, that makes a lot of sense. And there's certainly lots of good arguments for why these programs are useful. But when economists look at that, they see something different. They see that you're actually paying people to stay poor. Right. So when they designed the Earned Income Tax Credit, economists were coming from a totally different direction.

They did an economist mind flip. They said, if the ultimate goal is to help people move up the economic ladder, then you have to pay them to move up the economic ladder. Somebody like Mirjana Choa, when she made $9,000, she got a $3,000 bonus. When she made $15,000, four years later, she got $4,000 from the EITC. Then that's the sort of economist mind flip, right, is the more you make, the more the EITC pays you. And that's a pretty radical change. You know, it was in the 90s that the EITC was created in a big way, right? And that was when we were reforming welfare as we know it. So welfare up until that point had for the most part

given people money because they proved that they had need and then it would take that money away if they started working and made too much money. So the EITC was this new approach to that problem. Yeah, it's this very delicately designed equation. You start out, you make more and more money, you get bigger and bigger bonuses, and then at some point you peak somewhere, say, between $12,000 and $20,000, depending on how many

kids you have. And then the bonuses start to get smaller again. But even when the bonuses are getting smaller again, they're not getting smaller so quickly that it makes you want to stay at a smaller salary. Right. And for Ochoa, this was like magic. When she first started getting the EITC, she was working part time. She was caring for a son who was in special ed.

She was on food stamps, and she was in debt from her divorce. And since then, with help from the EITC, she has paid her debt. She's gotten off food stamps. She went to school for accounting. And when she was unhappy with the Newark High School her son was going to have to enroll in, she managed to even move to a better school district. I found an apartment there, and I changed my own life. Could you have moved to a nicer neighborhood

with nicer schools without the earned income tax credit? No. No, no, no. Because my income is low. It's low income. OK, so we've got this delicately designed equation that actually pays you more the more money you make to help you move up the economic ladder. And then we have the second magic ingredient that makes the earned income tax credit so

successful. And the second is that it just pays you cash. It follows a very simple idea that economists love, which is that the best way to help poor people is to give them cash and trust them how to spend it best. And this kind of aid to poor families in economics is called a cash transfer. And right now, the majority of the assistance the government offers to poor people is not cash. We're not spending a lot of time handing over

cash. The government is giving poor people things like health care or vouchers for housing, food stamps, things called in-kind transfers. There are a lot of economists out there who really prefer the cash transfers to the in-kind transfers and it's not just economists. If you ask someone like Reo Sorio, recent father of these two twin boys you hear napping loudly in his living room, cash is the only kind of help he wants. I know, I know how to spend it. For everybody else, I can't speak for everyone else,

I'm not sure. What he needed was some cash to invest in his business. He wanted to start a luxury car service, get a fancy ride to shuttle around actors and diplomats. And he knew a lot of people like that because of his years working in the hotel industry. So when his twins were born he actually cashed out his 401K to buy this fancy car. He started his business and is going along but slowly and he had just run out of all of his savings when he found out that he qualified for the earned income

tax credit this year and he said he was quote delighted. I was like wow that's incredible that's that's really that's a really nice number. That's more than a third of what you made last year right? Definitely is. And it was incredible. So you're like, whoa, we're going on vacation. Not at all. Not at all. I'm just looking, I'm just trying to focus on the future. Hopefully, my business will bring me plenty of vacations later on down the line. So we've got two EITC poster children here, Ochoa and Osorio, and there are millions more whose lives have really and truly been changed by this policy. But before we get too happy, Hannah, I do need to say that the EITC doesn't solve every

problem. First of all, it only helps people who are working. If you don't or can't work, there's nothing in it for you. Some people that should get it don't, and some people game the system. They get it when they shouldn't. And there are a lot of economists who argue that if you didn't have in-kind transfers like food stamps or government healthcare, the EITC wouldn't be so successful. It has to exist alongside those other programs.

Because people, a lot of people who are on EITC are also getting food stamps or getting those kinds of supports as well at the same time. Yes, it's different in every state, but certainly people benefit from both at the same time. Okay, so maybe those things help the EITC be super successful. But still the things that economists love about it, those things really do work. Marianne McCune and Hannah Jaffe-Walt from 2013. In the United States and all around the world, the rich get taxed at a higher rate than the poor.

But it took a while in the United States to come around to this sort of system that we have now. The founders of the United States did not include the idea of an income tax in the Constitution. And it wasn't until the Constitution was amended in 1913 that we got what we know as a permanent progressive tax system. Professor Derek Hamilton, what does that mean? It's progressive.

And you know, this doesn't mean politically progressive. It means economically progressive. Essentially it means the more you have, the higher the tax rate you have to pay. And in the old days, there was this really wide range. If someone was poor, they would maybe not pay anything in taxes. But for the very richest of Americans, at a certain point during the last century, I think their marginal tax rate was up to 70% on that very last dollar that they earned. This is a classic example of a progressive tax code.

But some American taxes are regressive. What's a regressive tax and what's an example of that? A flat tax is a regressive tax. Everybody pays 12%. Everybody pays 12% of their income, that's regressive. Because some people just have lower incomes. When we think about consumption taxes, those are regressive taxes.

Consumption taxes meaning like sales tax, a sales tax, everybody who buys a bagel in New York City pays, I think it's like almost 9% of the price tag, something in there getting up to 9% of bagel doesn't mean very much to me, perhaps, but it might mean a lot to somebody who's making a very low wage. Yeah, if a bagel costs $10, that dollar that goes towards taxes for somebody who earns $1,000 a week is much less than somebody who earns $100 a week.

So we have this progressive income tax code in the United States, and maybe you can say we do it because it's the right thing to do. But there's an economic way to think about progressive taxation, and that's through this concept called marginal utility. Marginal utility is the use that you get out of every extra dollar, let's just say. You know, you hand me a dollar, eh, eh, put it in my pocket, maybe send it through the wash, maybe put it in the bank account. I won't necessarily spend it because I have extra money.

Or you hoard it. You save it away. Or if you give a single dollar to someone who is making below average wages, they're more likely to spend it, or as we heard in the story, invest in their business, or even go to Disneyland. How does this marginal utility play into thinking about taxes? Is it literally

that like a dollar means less to me than it does to them? You know, the concept of marginal utility is often thought about in an individual perspective. And indeed, there is this other concept in economics called diminishing returns. Explain that. It simply means the more you have of something, having an additional unit of it at some point begins to tail off in terms of increasing value to you. So we can give a simple example. If you have $100 and you get an additional dollar, well, going from 100 to $101 might be less valuable to you than going from, say, one dollar and getting an additional dollar.

Don't need money. Yeah. So, and we can think of it in a literal sense in terms of being able to simply buy things. When you want to buy food, for example, if you have a whole lot of money, getting an additional dollar is not going to make that much of a difference in your consumption habit for food. But if you're lower income, getting additional dollars or an additional dollar will indeed lead to a bigger effect

in terms of what you can actually consume. So if you're building a tax code and you know this economic principle, do you literally think, well, not that I'm taking from the rich and giving to the poor, but you're thinking like a dollar means less to a rich person than it does to a poor person? Well, if you ask them, they might tell you, no, it means the same to me. But also in economics, we know that revealed preference often happens through some behavioral thing. Don't tell me what you value

Show me what you value, but we can go a little deeper Robert. We actually get to define value we actually get to use our tax code we get to as a Society make choices of what we value so we may not like the fact that Poor people simply don't have enough money to eat So as a society we can ensure that people have enough money to eat. And furthermore, not only will they have enough money to eat, they can use that additional money in ways to invest in their own productivity that becomes more valuable than that single one dollar would have been to somebody who's already wealthy.

And as we heard from the earned income tax credit story, people across the political spectrum, they're okay with that. Coming up on our taxing episode of Planet Money Summer School, if the tax code can send money to the poor and even help them invest in their own futures, what other magical things can it do? Can it save the planet after the break? Okay class, it's about to get nerdy in the summer school. We're going to talk about a dead economist, an impossible to understand equation, and somewhere in there a way that

the government can nudge businesses to do what's right for society. It's a case study from Sarah Gonzalez and Jacob Goldstein, and it's the story of Arthur Pigou and the thing that he invented called Pigouvian Taxes. Pigou was born in England in 1877. Okay, sounds like the beginning of a story. And for 35 years, Pigou was the only professor of economics at Cambridge University. And he started when he was really young, 30. Everything we know about Pagu is kind of patchwork-y because Pagu didn't want us to know about

him. Nahid Aslanbegi is a Pagu expert, has been studying Pagu since the 80s, wrote a book on Arthur Cecil Pagu. I think he thought his life would be subject to a lot of scrutiny after his death. So he destroyed his private correspondence. He was a very private man. Pagoo loved the outdoors. He was a serious mountain climber, would show up to fancy economics lunches in his climbing

clothes with an ice axe and all of the- Sounds compelling. That's compelling. That's tough. But Pagoo cared about the world and he cared about people. He cared about people living in poverty, kids working in factories, maternity leave. He wanted mothers to get maternity leave. A hundred years ago. Yes.

How progressive of Pagoo. Yes, he was a progressive, like a lot of the late Victorians. So Pagoo loved the outdoors and he was living near London at this time, the was a progressive, like a lot of the late Victorians. So Pagoo loved the outdoors, and he was living near London at this time, the early 1900s, when air pollution had become a huge problem. They're burning coal, right? And it's like, you see those old pictures where it's like dark in the middle of the day.

It's like worse pollution than you can imagine now. Yeah, and the smog was called at the time London fog. Some people called it pea soup. It looked like pea soup if you make split pea soup with yellow split peas. It was thick. It covered everything. It was an oily substance that covered furniture.

Enter your rooms. You would breathe it. It killed people. it killed animals. And Pagoo thought about this not just as an outdoorsman, but as an economist. As an economist, he also saw the cost of Lendenfog. He thought it would increase healthcare costs, it would affect vegetation, livestock,

it would wreck your furniture, everyone would have to buy new furniture, everyone had to wash their clothes more often. Those are all costs. And the people burning the coal weren't going to be paying for this. Innocent bystanders would. This is a problem economists have since come to call a negative externality, right? Negative because it's bad, it's negative, and external because it is some innocent third party being affected. It's not the company burning the coal to make the product,

and it's not the person buying the product. It's just all the random people who have to breathe the polluted air. All the people who are external to the buying and selling of the product. And Pugu was the person who gave us this whole framework for thinking about negative externalities. And to be clear, Pugu didn't discover that sometimes private companies do things that hurt society, but what Pagu did was come up with a solution to the problem.

And he laid out this solution in this key graph in a book he published called Wealth and Welfare. And then once that came out, everyone was like, great, Pagu, thanks, we got it. Instant fame. Now, economists of 1912, they weren't quite ready for Pagoo's graph. Well, they were baffled by it. Some people criticized it.

And in the future editions of his book, I think he eliminated that graph. He didn't use it anymore. He took it out? He took it out because there were complaints. What were they complaining about? It was too complicated. His vocabulary, you have to really work through it very hard to understand what he's saying.

Like anyone who writes anything in the early 1900s? Some are worse than others. I think his text is worse. Oh, okay. Interesting. Yes. Okay. So here, Jacob is his terrible, not easy interesting. Yes. Okay, so here Jacob is his terrible,

not easy to understand graph. Okay. Apart from this condition, O N may be either greater or less than O M, according to the relations that subsist between the curves where O N is blah, blah, blah. And then there is a graph that is just brutal, just totally unintelligible.

Yeah, and Nahid was basically like, you will never understand this graph. Okay, fair enough. I'll give up now. Don't even try. Okay. So luckily for us, like later on economists simplified Pagoo's famous graph. So here is the more easy to understand Pagoo graph. I'm waving my hands.

Okay. We're doing graphs on the radio. Yes, it's hard, but we're planning money. We're going to do it. Okay. So there's an x-axis and a y-axis. The classic econ graph. Vertical axis is price. The horizontal axis is quantity. Okay, so far so good. There's these two lines going up into the right basic, you know, positive slope lines on the graph and one of them says PMC. Just private marginal cost. Okay, so private marginal cost. This is like the classic idea of cost, right? Like let's go back to the Pagu London Fog early 1900s world.

Sarah say you have a factory in London. You are burning coal to make your products, whatever you're making. Socks. Okay. So this line, the private marginal cost line is the cost for you to make socks in your coal burning polluting factory That's the private marginal cost. Okay, and then this other line says SMC SMC that's the social marginal cost and that would be the cost on society for me to make my socks So that one is not only the cost to you of whatever the wool and the labor and the machines

But also the cost of all of the pollution that your factory is emitting. Exactly. That's the cost of everyone who gets sick from my pollution and everyone who has to wash their clothes and buy new furniture. That's the social cost. And in this graph, the social cost, the cost on society is higher than the private cost. So another way to say this then is when there is a negative externality, right? When you're running your polluting factory to make your socks, the price you're selling those socks at is tooality, right? When you're running your polluting factory to make your socks, the price you're selling those socks at is too low, right? Because if I'm buying your product, I'm paying just the private cost for those socks. But the real cost when

you take into account externalities should be higher. The socks that you're selling should be more expensive to take into account the cost of the pollution to society. That's his famous graph. And what this graph said for the first time to the whole entire world was that you had to put a price on these problems or they would never be solved. You could calculate that cost and force the guilty parties to pay for it. Like figure out how much London fog is costing people and then force the companies burning the coal, creating the London fog to pay for it,

not the innocent bystander. That's what makes it a Puguvian tax. There are plenty of other taxes on things that seem bad, like cigarettes and alcohol, but those taxes are meant to prevent you, the drinker or smoker, from drinking or smoking too much. It's not intended to do anything for innocent bystanders. If you wanna put a Puguvian style tax on alcohol,

a government would have to say, okay, what problems does alcohol cause third parties? Crime. When people drink more, they're more likely to commit crimes. Would a government have to say, okay, how much is crime costing us as a result of alcohol? Yes. So how do you know how much crime has been caused by alcohol?

Well, that's the million dollar question, isn't it? It's really hard to measure how much crime brought on by alcohol specifically is costing taxpayers, or how much smokers who get lung cancer and don't have health insurance cost taxpayers, or how much pollution costs society. ["The Big Bang"] Sarah Gonzalez and Jacob Goldstein from a show we did in 2019.

This idea, the Paguvian Tax, was later used to develop carbon taxes in countries like Canada, New Zealand, and Scandinavia. They figured out what burning fossil fuels cost society in terms of climate change and added that as a tax to companies that sell and produce those fuels. But there are other Paguvian Taxes. If you'd like to see one in action, you can come drive in New York City in Manhattan. There is a new congestion tax on cars who drive at a certain part of Manhattan, which is meant to reduce the negative externality of crowded roads, externalities like lost

time, pollution, noisy streets. And guess what? After they put the tax in, travel times on the streets of Manhattan have improved. The extra tax money is being spent on public transit. We'll talk about how these taxes work and the unintended consequences with our professor after the break. So we are back with our professor Derek Hamilton from the new school. Hey Derek. Hey there. You're so excited by taxes.

Oh yeah, I get excited. Let's go to the very basic economic principle of using taxes to change behaviors, whether it's corporate or individual. Why does putting a tax on something create less of it? It makes something more or less expensive. It's pretty simple, right? It's like supply and demand, and the government steps in,

and makes some things more expensive and some things less expensive. And we are more likely to do the thing that is less expensive. That's right. How does the government decide what it should put these taxes on in order to influence people? You know, you can make the negative externality argument by making the case that if somebody gets more sickly

from the types of food they consume, like sugary drinks, that that becomes a burden on our health care system. But like all taxes, it's often done due to political process. These taxes often work, but there's ways in which they don't work. So one way is that people find a way to avoid the taxes. Maybe they don't have a sugary drink,

but they spend it on something else that's bad for them. So you always have to think with these taxes, you're not just discouraging one thing, you may be encouraging people to shift to another thing. We use the word unintended consequences. It might divert activity in one area, but sometimes that activity will reappear in other areas in ways that we may have intended and also unintended.

People are so, so clever. I'm curious, professor, as you look around society, is there something that you think has a negative externality? It's creating problems for society that is not priced in that we should put a Puguvian tax on? Well, frankly, I got a pet peeve with all the junk mail I get,

both electronic and paper. We just had an election here, yes. So from a personal perspective, I would love that there was not a zero cost of sending emails that I certainly don't want to read. Frankly, I wish we tax some of the mass bulk mailing that I get on a daily basis and have to dispose of,

and surely it's not good for the environment. This is genius. And we learned from this episode that you have to kind of work it out. Like what is the cost to society? How much time are you spending, right? Going through junk mail. So we'd have to figure that society wide.

We'd add that to the cost of sending junk mail. And then we'd have to like figure out a way to maybe spend that money for alternatives, right? So how could we spend that money if we tax these junk mailers? I mean, one way is we could use some of that money to help with our recycling cause. Exactly. That's great. I was going to say library so that people read more valuable material. But yeah, yeah, yeah. These are the sort of principles here of the Puguvian tax. Exactly.

One of the things we love to do here is vocabulary words. It's so funny when I was in high school, I hated vocabulary words, but now like I do it for a living, um, because I think it does focus us on what exactly can we take with us out into the world from this episode? One of our very basic vocabulary words is progressive taxation. What does that mean? Progressive taxation would suggest that those who can least afford to pay the tax pay

a lower rate than those who can most afford to pay it. Marginal utility. I feel like we're in Econ 101. What is marginal utility? I mean, utility is a concept to represent value, and marginal is an additional item, a small change. So marginal utility, if we add them together, how does your value from the item change from one additional unit?

If you've been in Econ 101, you know they will bring up the example of pizza slices. By the time you get to the third or fourth slice, your marginal utility may be not as much from an extra slice of pizza. In the episode on Pagu, we talked about negative externalities. What's a negative externality?

It's the additional cost borne on to society from some private actions. And the key is the private action is not priced into the product. You're basically getting the product for cheap because it doesn't factor in the terrible stuff it does. That's right. You don't know how many hours you're costing of Derek's time when you send him junk mail. It's a real societal cost. Stop sending me junk mail. And as our final vocabulary word, the way to fix a negative externality is a Paguvian tax. Put the real cost of societal harm into the price of the product and let the market decide if it's worth it.

Thanks so much, Derek Hamilton from the New School. It was great to have you in. Thank you, sir. Appreciate you. Students, before you go, make sure you get your ticket to our live graduation event in New York City. It's on August 18th. You can wear a gown, bring your parents, and compete to become the Class of 2025 Summer School Valedictorian. Put that on your resume. It's on August 18th and the ticket info is in the show notes.

Do it now. If you're a Planet Money Plus subscriber, you get a discount and an access to time travel. Well, a very minor form of time travel. You get each summer school episode a week early. Next week on summer school, we've done taxes. How about spending? Government makes a lot of choices about how to spend that tax money.

Why does it pay for some things and not others? Coming up next week. Summer School is produced by Eric Mendel and edited by Alex Goldmark. It was fact-checked by Emily Crawford and C.R. Whitehouse. Devin Meller is our project manager. I'm Robert Smith. This is NPR. Thanks for listening.