Unit 8 · Trade, Taxes and the World Economy

Imagine two small countries, Aland and Bland, that each make only two things: shirts and wheat. In one hour of work, a worker in Aland can sew 4 shirts or grow 2 bushels of wheat. In one hour, a worker in Bland can sew 1 shirt or grow 1 bushel of wheat. Aland’s workers make more shirts per hour and more wheat per hour. Economists say Aland has an absolute advantage in both goods.

An absolute advantage means you can produce more of something than someone else using the same amount of a resource, such as an hour of labor or an acre of land. It is the most natural way to compare producers, and it is the way Adam Smith described trade in 1776. If your neighbor bakes better bread and you fix better bicycles, you each do what you do best and swap. Both of you end up with better bread and a working bike.

But this leaves a puzzle. In our example Aland is better at both things. If absolute advantage were the whole story, Aland would have no reason to trade with Bland at all. It could just make everything itself. Yet countries in exactly this position trade with each other all the time. The United States, with some of the most productive workers in the world, imports goods from countries with far less productive workers.

The answer to the puzzle is the subject of the next lesson. For now, get the first idea straight. Absolute advantage answers the question, who can make more? It does not answer the question, who should make what? To answer that one, we have to look at what each producer gives up, which is the idea of opportunity cost you already know.

Go back to Aland and Bland and ask a different question. Not who can make more, but who gives up less. In Aland, an hour spent growing 2 bushels of wheat is an hour not spent sewing 4 shirts. So each bushel of wheat costs Aland 2 shirts. In Bland, an hour growing 1 bushel is an hour not sewing 1 shirt. Each bushel of wheat costs Bland only 1 shirt. Bland gives up less to grow wheat.

Now flip it. Each shirt costs Aland half a bushel of wheat, since 4 shirts equal 2 bushels. Each shirt costs Bland a full bushel. So Aland gives up less to make shirts. The country with the lower opportunity cost for a good has the comparative advantage in that good. Bland has the comparative advantage in wheat. Aland has the comparative advantage in shirts, even though Aland is better at both in absolute terms.

This is the idea David Ricardo worked out in 1817, and it is one of the few results in economics that almost every economist accepts. A country cannot have a comparative advantage in everything, because opportunity costs are ratios. If Aland gives up fewer shirts per bushel, it must give up more bushels per shirt. Somebody always has the lower cost in each good, so there is always a basis for trade.

The common mistake is to compare raw output and stop there. Students see that Aland makes more of both and conclude Aland should make everything. Check yourself by computing the opportunity cost of each good in each country, as a ratio, and then compare the ratios. The lower ratio wins that good. A country should specialize in what it does at the lowest cost to itself, not in what it does best compared with others.

Let us prove the gain with numbers. Suppose a worker in each country has an 8-hour day. Without trade, each splits the day. The Aland worker spends 4 hours on shirts and 4 on wheat: 16 shirts and 8 bushels. The Bland worker does the same: 4 shirts and 4 bushels. Together the two workers produce 20 shirts and 12 bushels. That is the total the world gets when each country tries to make both things.

Now let them specialize by comparative advantage. Bland spends all 8 hours on wheat and grows 8 bushels. Aland shifts toward shirts: 6 hours on shirts makes 24, and 2 hours on wheat makes 4 bushels. Together they now have 24 shirts and 12 bushels. The same two workers, the same day, and 4 more shirts with no less wheat. Nothing was invented. The gain came only from putting each hour where it cost the least.

Trade shares the gain. They agree on terms of trade of 1.5 shirts per bushel, which lies between the two opportunity costs of 1 and 2. Bland sends Aland 4 bushels and gets 6 shirts back. Bland ends the day with 4 bushels and 6 shirts, instead of 4 and 4. Aland ends with 18 shirts and 8 bushels, instead of 16 and 8. Both countries have more of at least one good and no less of the other. That is the gains from trade.

Notice why the price mattered. If Aland had demanded 2 shirts per bushel, Bland would be no better off than growing shirts itself, so it would refuse. If Bland demanded 1 shirt per bushel, Aland would refuse. Any price between the two opportunity costs leaves both better off. In the real world millions of prices are set this way, in markets, and the same logic explains why an Illinois farmer sells soybeans abroad and buys a phone made overseas.

An export is anything made in one country and sold to a buyer in another. Illinois soybeans on a ship to Asia are exports. So is a Chicago software company’s subscription sold to a firm in Germany, because services count too. An import is the reverse: anything made abroad and bought here. The phone in Naperville, a car built in Mexico and a vacation a Chicago family takes in Italy are all imports.

The trade balance is simply exports minus imports for a country over a period, usually a year. Suppose in an example year a country exports $2,000 billion of goods and services and imports $2,500 billion. Its trade balance is $2,000 billion minus $2,500 billion, or negative $500 billion. A negative balance is called a trade deficit. If exports had been larger than imports, the positive balance would be a trade surplus.

The United States has run a trade deficit every year for roughly fifty years. It sells enormous amounts abroad, but it buys even more. Illinois follows a similar pattern in goods, exporting farm products, machinery and chemicals while importing electronics, vehicles and oil. Because the numbers are so big, news reports usually give them in billions and compare them to the size of the whole economy.

One habit worth building: check which direction the money flows. When an Illinois farmer sells soybeans to a buyer in Japan, the beans go out and dollars come in. When a Chicago store buys phones from a factory in Vietnam, phones come in and dollars go out. Exports bring money in; imports send it out. The trade balance is the net result, and a deficit means more money went out for goods and services than came in.

People often hear the word deficit and assume it means loss, like a business losing money. A trade deficit is not that. When an American buys a $600 phone from a factory abroad, the American gets a phone worth $600 to her and the factory gets $600. Nobody lost. The deficit records only that, added up across the whole country, Americans bought more goods and services from foreigners than foreigners bought from Americans.

So where do the extra dollars go? A foreign factory that earns dollars can spend them on American goods, which would be an export. Or it can invest them in America by buying a Treasury bond, shares of an American company or a warehouse in Joliet. Every dollar that leaves for an import comes back one way or the other. A trade deficit in goods and services is matched by a surplus in capital flows: foreigners investing more in the United States than Americans invest abroad.

This is why economists are split about whether a trade deficit is a problem. On one side: it means foreigners are lending to us and buying our assets, and that borrowing has to be paid back with interest someday. A deficit can also fall hardest on particular industries and towns. On the other side: the investment builds factories and funds the government, and a country whose people and firms are attractive to invest in will naturally run a deficit. Both sides agree the deficit alone does not tell you whether a country is doing well.

Watch for two common mistakes. First, a trade deficit is not the same as the federal budget deficit, which is government spending minus tax revenue. They are different numbers about different things, even though both use the word deficit. Second, a deficit with one country means little on its own. The United States can run a deficit with one trading partner, a surplus with another, and the overall balance is what economists study.

Illinois is one of the biggest exporting states in the country, and its exports show comparative advantage at work. The state has some of the richest farmland on Earth, so it is regularly among the top two states for soybeans and corn. It has a long history of building heavy machinery, from construction equipment to farm tractors. And it has chemical and pharmaceutical plants. These are the goods that Illinois can make at a lower opportunity cost than most of the world.

Geography matters too. The Illinois River flows into the Mississippi, which carries barges to the Gulf of Mexico. Chicago is the busiest rail hub in North America, where lines from both coasts meet. O’Hare handles enormous amounts of air cargo. Because moving goods is cheaper here than in many places, businesses that need to ship things choose Illinois, and that in turn strengthens its advantage.

Illinois’s largest trading partners are its neighbors. Canada and Mexico buy more from Illinois than any other countries, which is why trade agreements with them matter so much to the state. Trucks and trains cross those borders every day carrying machinery, parts and food. Farther away, buyers in Asia take a large share of the state’s soybeans, and Europe buys chemicals and medicines.

Trade cuts the other way as well. When another country puts a tariff, a tax on imports, on American soybeans, Illinois farmers feel it first, because the buyers turn to soybeans from Brazil instead. When the price of imported steel rises, Illinois machinery makers pay more for their inputs. A state that sells so much to the world is also one of the states most exposed to what happens when trade slows. That exposure is the reason Illinois politicians of every stripe watch trade policy closely.

A tariff is a tax on an imported good, collected at the border. Suppose an imported bicycle sells for $200 and the government sets a 25% tariff. The importer must pay $50 in tax, so the bike now costs $250 to bring in and the store price rises toward $250. American bike makers who were losing sales at $200 can now sell at close to $250 too. That is the point of a protective tariff: it protects domestic producers from foreign competition.

Trace who gains and who pays. Consumers pay: everyone who buys a bike, imported or not, pays up to $50 more, and some people who would have bought at $200 do not buy at all. The government gains: it collects $50 on every imported bike that still comes in. Domestic producers gain: they sell more bikes at a higher price. When economists add up all three, the loss to consumers is bigger than the gain to the treasury plus the gain to producers. The difference is called the deadweight loss of the tariff.

Why is the loss bigger? Because the tariff causes two kinds of waste. Some bikes are now built at home for $240 that could have been bought abroad for $200, using up $40 of resources for nothing. And some people who valued a bike at $220 no longer buy one, losing a deal that would have made them better off. Neither of those losses shows up as anyone’s gain.

The question of who really pays a tariff is the same tax incidence question you met with sales taxes. The importer writes the check, but it passes most of the cost to the buyer through a higher price. How much passes through depends on elasticity. If buyers have few substitutes, they absorb nearly all of it. If the foreign seller badly needs the American market, it may cut its price and absorb some. In most studied cases, most of a tariff lands on the buyers in the country that imposed it.

A quota is a legal limit on how much of a good may be imported in a period. Instead of taxing each bike, the government might say: only 50,000 imported bikes this year. If Americans wanted 100,000 imported bikes at the world price of $200, the quota creates a shortage of imports. The price rises until buyers want only what is allowed, plus whatever domestic makers add. In our example the price might settle near $250, the same as under the tariff.

The difference is where the extra $50 per bike goes. Under a tariff, the government collects it. Under a quota, the firm that holds the right to import collects it, because it buys at $200 abroad and sells at $250 here. Those import rights become valuable, and if they go to foreign sellers, the money leaves the country entirely. This is why most economists, if forced to choose, prefer a tariff to a quota of the same size: at least the revenue stays home.

Countries also slow trade in quieter ways. A voluntary export restraint is a quota in disguise: one country agrees to limit its own exports so the other will not impose a tariff. Safety, health and labeling rules can be genuine protections or can be written to keep out foreign goods. Subsidies to domestic producers let them undercut imports. Long customs delays act like a tax on time. Together these are called non-tariff barriers, and they are often harder to see and argue about than a tariff rate.

The economic effect of every barrier is the same in direction. Prices rise for consumers, domestic producers sell more, the quantity traded falls, and some value is lost. The barriers differ in who captures the price increase and in how visible they are. When you read about a trade dispute, ask two questions: what tool is being used, and who gets the extra money?

If trade barriers cost consumers more than they gain producers, why does nearly every country use them? Serious arguments exist, and a fair student should know them. The oldest is the infant industry argument. A new industry in a country may not be able to compete yet with established foreign firms. Protect it for a while, the argument goes, and it will grow, learn and eventually stand alone. Several countries that industrialized quickly, including the United States in the 1800s, used tariffs in this way.

A second argument is national security. A country may not want to depend on a rival for steel, computer chips, medicine or food, even if imports are cheaper. If a war or a crisis cut off the supply, the cheapness would not matter. Most economists accept that this argument justifies some protection for a narrow set of truly essential goods. The disagreement is about how wide that set really is, since almost every industry claims to be essential.

The most common argument is jobs. When a factory closes because imports undercut it, the workers, their families and their town lose. Economic theory says the gains from trade are large enough that the winners could compensate the losers. In practice that compensation is often small and late. A worker who spent twenty years making furniture cannot easily become a software engineer at fifty. Protection that slows the change gives towns time to adjust. Critics answer that it also freezes resources in industries where they no longer belong.

There are two more arguments you will hear. One is fairness: if another country subsidizes its exporters or blocks our goods, our barriers are a response, and the threat of them is a bargaining tool. The other is that trade can be used to pressure countries over human rights or environmental damage. Each of these has some force. Each is also easy to abuse by an industry that simply wants less competition. The economic way to judge them is to ask what the barrier costs consumers and whether a cheaper tool would reach the same goal.

Start with the arithmetic from the tariff lesson: consumers lose more than producers and the treasury gain. Studies of real tariffs regularly find that each job protected costs consumers far more than that job pays. A tariff that saves a $50,000 factory job by raising prices $200,000 across the country is a bad trade even for the workers, since the same money could retrain three of them and still leave the country ahead. Economists call this the cost per job saved, and it is usually startling.

Second, most imports are not finished goods for shoppers. They are intermediate goods: steel for tractors, parts for cars, chemicals for medicines. A tariff on steel helps steel mills but hurts every factory that uses steel, and those factories employ many more people than the mills do. Illinois machinery makers are a clear case. Protect one link in the chain and you tax all the links after it.

Third is retaliation. When one country raises tariffs, its trading partners usually answer with tariffs of their own, aimed at the first country’s most politically sensitive exports. American farm goods, including Illinois soybeans, are a frequent target. The Smoot-Hawley Tariff of 1930 raised American tariffs sharply during the early Great Depression. Other countries retaliated, world trade shrank, and most economists believe the tariff made the Depression worse, even if it did not cause it.

The honest summary is that economists broadly favor open trade while agreeing that it has real losers who deserve real help. The disagreement in public life is about how much weight to give the losers, how much to trust the arguments for exceptions, and whether help for displaced workers will actually arrive. Those are partly questions of values, not just economics. What economics can do is put numbers on the costs so that the choice is made with open eyes.

A country could lower its tariffs alone, and economists say it would gain from doing so. Politically that is hard, because the losers are visible and the winners are scattered. A trade agreement solves part of the problem. Two or more countries agree to cut barriers at the same time. Now the deal has visible winners at home, the exporters who gain access to foreign markets, and they push for it as hard as protected industries push against it.

The most important agreement for Illinois is the one with Canada and Mexico. The North American Free Trade Agreement took effect in 1994 and removed most tariffs among the three countries. It was replaced in 2020 by the United States-Mexico-Canada Agreement, which kept most of the structure and added new rules for cars, digital trade and labor. Because Canada and Mexico are Illinois’s biggest customers, changes to these agreements matter more in Illinois than in most states.

A free trade area removes tariffs among members but lets each keep its own tariffs on outsiders. A customs union goes further and sets one common tariff for everyone outside. A common market adds free movement of workers and money. The European Union is the largest example of the deeper kind. Each step gives up more national control in exchange for more integration, which is why each step is also more controversial.

Agreements always contain compromises. A deal that opens markets for Illinois machinery may also open American markets to foreign farm goods, and the affected farmers object. Rules about where a product must be made to count as domestic, called rules of origin, fill hundreds of pages. Judge an agreement the way you judge a tariff: who gets more market access, who faces more competition, and what happens to the prices consumers pay.

After the tariff wars of the 1930s and the Second World War, countries wanted rules to keep trade from collapsing again. In 1947 a group of them signed the General Agreement on Tariffs and Trade, or GATT, and spent the next decades negotiating round after round of tariff cuts. In 1995 the GATT became a permanent organization, the World Trade Organization, based in Geneva. Today more than 160 countries belong, and together they carry out nearly all world trade. China joined in 2001, a change that reshaped global manufacturing.

The WTO rests on a few core rules. The most important is most-favored-nation treatment: a member must offer every other member the lowest tariff it offers to any of them, with exceptions for free trade areas. Another is national treatment: once a foreign good has cleared customs, it must be treated like a domestic good. Members bind their tariffs, promising not to raise them above agreed ceilings without compensating others.

When one member believes another has broken the rules, it can bring a dispute. Panels of trade experts hear both sides and issue a ruling. If the losing country does not comply, the winner may impose retaliatory tariffs of an approved size. The WTO has no police and cannot force anyone; its power comes from the fact that members want the rules to hold for everyone else. In recent years its dispute system has weakened as some large members have blocked appointments to its appeals body.

People argue about the WTO from every direction. Supporters say it kept the world from repeating the 1930s and gave small countries a way to challenge big ones. Critics on one side say it limits a country’s freedom to protect its workers and environment. Critics on another side say it does too little about subsidies and unfair practices by large exporters. The standard economic view is that shared rules make trade more predictable, which raises the gains from it, and that the rules should be improved rather than abandoned.

An exchange rate is the price of one country’s money measured in another country’s money. If 1 dollar buys 20 pesos, the exchange rate is 20 pesos per dollar. You can flip it: 1 peso buys 1/20 of a dollar, or 5 cents. Every day, banks, businesses and travelers exchange trillions of dollars’ worth of currencies, and the rates move minute by minute like stock prices.

Work through a meal. A restaurant in Mexico City charges 300 pesos for dinner. At 20 pesos per dollar, that dinner costs an American 300 divided by 20, or $15. Now suppose the rate moves to 15 pesos per dollar. The same 300-peso dinner costs 300 divided by 15, or $20. Nothing changed in the restaurant. The dollar simply buys fewer pesos, so everything priced in pesos costs more dollars.

When a dollar buys more foreign money than before, we say the dollar has appreciated, or gotten stronger. When it buys less, it has depreciated, or weakened. Students often get the direction backwards, so check with the meal. At 20 pesos per dollar the dinner was $15; at 15 pesos per dollar it was $20. More pesos per dollar means a stronger dollar and cheaper foreign goods for Americans.

The same logic runs the other way for a Mexican traveler in Chicago. A $40 museum ticket costs 800 pesos when the rate is 20, but only 600 pesos when the rate is 15. A weaker dollar is a stronger peso, and it makes American goods cheaper for Mexicans. Every exchange rate is two prices at once, and whatever one side gains in cheapness, the other side loses.

Think of an Illinois soybean farmer selling to a buyer in Mexico. Suppose soybeans sell for $10 a bushel. At 20 pesos per dollar the Mexican buyer pays 200 pesos a bushel. If the dollar strengthens to 25 pesos, the same $10 bushel costs the buyer 250 pesos. Nothing about the beans changed, but they got 25% more expensive in Mexico. The buyer may switch to Brazilian soybeans instead. A strong dollar makes American exports harder to sell.

Now think of a Chicago store that imports avocados priced at 40 pesos each. At 20 pesos per dollar, each avocado costs the store $2. At 25 pesos per dollar it costs $1.60. The store can lower its price and sell more. A strong dollar makes imports cheaper, which is good for stores that sell them, for factories that use imported parts, and for every shopper who buys foreign goods.

So the same event, a stronger dollar, creates winners and losers inside the country. Winners: importers, consumers, travelers going abroad and businesses that buy foreign inputs. Losers: exporters such as farmers and machinery makers, American hotels and attractions that serve foreign tourists, and firms that compete with imports at home. A weaker dollar flips every one of those. That is why you will hear a business leader complain about the strong dollar while a shopper next to her enjoys cheap electronics.

Because a strong dollar makes exports fall and imports rise, it tends to push the trade balance toward a larger deficit. A weak dollar tends to shrink the deficit. This connects the two halves of the unit. When you read that the dollar has risen, ask who sells abroad and who buys from abroad, and you will know who is smiling.

A currency is bought and sold in a market, so its price obeys supply and demand. Who demands dollars? Anyone abroad who wants to buy American things: a Mexican company buying Illinois soybeans, a Japanese investor buying a Treasury bond, a tourist booking a hotel in Chicago. They must sell their own currency and buy dollars. When demand for dollars rises, the dollar appreciates, just as the price of anything rises when more people want it.

Who supplies dollars? Americans who want foreign things: a store importing avocados, an investor buying European stocks, the Reyes family exchanging $800 for pesos. They sell dollars and buy foreign currency. When Americans want more from abroad, the supply of dollars in the market grows, and the dollar depreciates. Trace any news story about the dollar back to one of these two curves.

Interest rates are the biggest short-run driver. If the Federal Reserve raises interest rates while other central banks do not, dollar bonds and bank accounts pay more. Investors around the world want them, so demand for dollars rises and the dollar appreciates. A rate cut does the reverse. Expectations matter too: if traders expect the dollar to rise next month, they buy it now, which makes it rise today. And a country with high inflation tends to see its currency depreciate over time, because each unit buys less.

Most major currencies, including the dollar, float: their prices move freely with the market. Some countries instead peg their currency, promising to hold it at a fixed rate to the dollar, and their central banks buy or sell reserves to keep it there. A peg gives businesses certainty but can break badly if the market pushes hard enough. The value of the dollar is also lifted by a special role: much of world trade and many foreign reserves are held in dollars, which creates steady demand for it.

Governments raise money in many ways, and economists sort taxes by one question: as a person’s income rises, does the tax take a bigger share of it, a smaller share, or the same share? Notice the word share. A rich person almost always pays more dollars than a poor person. What matters for this sorting is the percent of income paid, which economists call the average tax rate: total tax divided by total income.

Take two people, one earning $20,000 a year and one earning $100,000. Under a progressive tax, the share rises with income. Suppose the first person pays $1,000 and the second pays $20,000. The first pays 5% of income; the second pays 20%. The federal income tax works this way, with higher rates applied to income above certain levels. Under a proportional tax, sometimes called a flat tax, everyone pays the same share. At a flat 5%, the first pays $1,000 and the second pays $5,000. Illinois’s state income tax is proportional, a single rate of 4.95% on income.

Under a regressive tax, the share falls as income rises, even though dollars may rise. Sales taxes usually work this way. Suppose both people spend $10,000 a year on taxed goods and the sales tax is 6%. Each pays $600. For the first person that is 3% of income; for the second it is 0.6%. Lower-income households spend a bigger part of what they earn, so a tax on spending takes a bigger share from them.

Two cautions. First, a tax can look progressive on paper and be less so in practice, because deductions and exemptions change who pays. Second, judging a tax system means adding all the taxes together, since a regressive sales tax and a progressive income tax partly offset each other. Economists describe the shape of a tax with these words. Whether a tax should be more or less progressive is a question of values on which reasonable people, and economists, disagree.

Look at a pay stub and you will see several lines subtracted from gross pay. The largest for most workers is federal income tax. Congress created the modern version after the Sixteenth Amendment was ratified in 1913. The tax uses brackets: a low rate on the first slice of income, a higher rate on the next slice, and so on. A common mistake is to think that moving into a higher bracket taxes all your income at the higher rate. Only the dollars inside that bracket are taxed at that rate.

Here is the bracket idea with made-up rates. Suppose the first $10,000 of income is taxed at 10% and everything above that at 20%. A person earning $15,000 pays $1,000 on the first $10,000 plus $1,000 on the next $5,000, for $2,000 total. Her average tax rate is $2,000 divided by $15,000, about 13%. Her marginal tax rate, the rate on her next dollar, is 20%. A raise never leaves you with less take-home pay under a bracket system, because only the extra dollars face the higher rate.

The next lines are payroll taxes, listed as Social Security and Medicare, or together as FICA. The Social Security tax takes 6.2% of wages up to a yearly cap, and Medicare takes 1.45% with no cap. On a $1,000 paycheck that is $62 plus $14.50, or $76.50. Your employer pays a matching amount on top of your wages. These taxes fund retirement and disability benefits and health insurance for people over 65. Because the Social Security portion stops above the cap, payroll taxes as a whole are regressive at high incomes, though the benefits they fund are tilted toward lower earners.

Illinois adds its own flat income tax at 4.95%, so an Illinois pay stub has a state line too. Put together, a worker’s paycheck shrinks by federal income tax, state income tax and payroll taxes before she sees it. The amounts withheld are estimates. In the spring, filing a tax return settles the account: a refund if too much was withheld, a payment if too little.

Buy a $40 pair of shoes in Illinois and the register adds sales tax. The state’s base rate is 6.25%, and counties, cities and transit districts often add more, so the total in Chicago is higher than in a small downstate town. At 6.25%, the tax on $40 shoes is $2.50 and the total is $42.50. Sales tax is easy to collect, since stores do it at the register, and it is the largest source of money for many states. As you saw, it is regressive, which is why some states exempt groceries or medicine.

Own a house and you pay property tax each year, based on the assessed value of the land and building. Suppose a home is assessed at $200,000 and the local rate is 2%. The owner pays $4,000 a year. Renters pay it indirectly, because landlords build it into rent. In Illinois, property taxes are among the higher ones in the country, and they are the main source of money for local public schools. This is why school funding differs so much between towns with expensive homes and towns with cheap ones.

Governments also charge excise taxes on particular goods: gasoline, tobacco, alcohol. A gasoline tax of, say, 40 cents a gallon adds $6 to a 15-gallon fill-up. Excise taxes often do two jobs: raising money and discouraging the thing taxed. A gasoline tax that pays for roads charges the people who use them most. A tobacco tax raises money and lowers smoking, which is the externality idea from earlier in the course.

Every tax has three questions attached. What does it fund? Who actually bears it, remembering that the person who writes the check may pass the cost along? And what behavior does it change? A property tax that funds schools, falls partly on renters and encourages nobody to do anything different is a very different instrument from a tobacco tax that funds health programs, falls on smokers and reduces smoking. Sorting taxes this way is the economic way of thinking applied to government.

The average American produces and earns far more than the average person in most of the world. The usual measure is GDP per capita: a country’s total output divided by its population. The United States produces on the order of $80,000 per person per year. Some of the poorest countries produce less than $1,000 per person. Even after adjusting for the fact that food and housing cost less in poor countries, the gap is many times over. That gap, and what causes it, is the subject of economic development.

GDP per capita is an average and hides a lot, so economists add other measures. Life expectancy at birth tells you about health. Years of schooling and literacy tell you about education. Access to electricity, clean water and the internet tells you about daily life. The United Nations combines income, health and schooling into a single number called the Human Development Index, so that a country with a high income but poor health does not look better than it should.

Here is the hopeful part of the story. In 1990 roughly 4 in 10 people in the world lived in extreme poverty, which the World Bank defines as living on only a few dollars a day. By 2019 it was under 1 in 10. Most of that change came from fast growth in Asia, above all in China and India, where hundreds of millions of people moved from farms to factories and cities. The pandemic in 2020 pushed the number back up for a time, and progress in parts of Africa has been much slower.

A pattern to remember: small differences in growth rates become huge differences over decades. A country growing 2% a year doubles its income in about 35 years. A country growing 7% a year doubles in about 10 years. Over a working lifetime, the second country goes from poor to middle income while the first barely moves. So the question of development is really the question of what makes a country grow faster, year after year.

Output per worker rises when each worker has more to work with. Physical capital means machines, roads, ports, power plants and factories. A farmer with a tractor grows far more than one with a hoe. Building capital requires saving and investing, either by a country’s own people or by foreigners, which is one reason capital flows across borders matter. Human capital means the skills, knowledge and health of the workers themselves. A literate, healthy workforce can use better tools and learn new ones.

Technology multiplies both. The same worker with the same machine produces more when someone finds a better method, a better seed or a better way to organize the factory. Poor countries have an advantage here: they can adopt what rich countries already invented instead of discovering it themselves. That is how several Asian economies caught up so fast. Trade speeds the process, because it brings in machines and ideas and forces domestic firms to match the world’s best.

But many countries have savings, workers and access to technology and still stay poor. The missing piece is institutions: the rules of the game. Will the government or a powerful neighbor seize your farm if you improve it? Will a court enforce a contract with a stranger? Can a business get a license without paying a bribe? Where property is secure, contracts hold and corruption is limited, people invest and build. Where they are not, people hide wealth, keep businesses small and stay away from long-term plans.

Economists disagree about how much weight to give each ingredient and about the best policies to build them. Some emphasize open trade and markets, some emphasize public investment in schools and roads, some emphasize political stability first. Almost all agree on a few things. War and civil conflict destroy growth. Hyperinflation destroys it. Educating girls as well as boys pays off in every measure. And there is no case of a country becoming rich while cut off from the rest of the world.

Poverty and inequality are related but not the same. Poverty is about having too little. The United States sets a poverty line, an income below which a household is counted as poor, adjusted for family size. For a family of four it has been around $30,000 a year in recent years. In recent years roughly 11 to 12 percent of Americans have lived below the line, with higher rates for children and for some groups. Government programs such as food assistance, tax credits for working families and housing aid are not counted in the official measure, so a second measure that includes them shows lower poverty.

Inequality is about how far apart incomes are, whether or not anyone is poor. A simple way to see it is to line up every household by income and cut the line into five equal groups, called quintiles. In an example economy, the bottom fifth might receive 4% of all income while the top fifth receives 50%. Economists also use a single number, the Gini index, that runs from 0, where everyone has the same income, to 100, where one person has everything. The United States has higher inequality than most other rich countries and lower than many developing ones.

The two can move in different directions. Fast growth can lift millions out of poverty while the richest gain even faster, so poverty falls and inequality rises. That is roughly what happened in China. A deep recession can leave inequality unchanged while poverty rises, because everyone loses together. When you read a claim about the economy, ask which of the two it is about.

What to do is one of the most argued questions in economics and politics. Some emphasize growth, since a growing economy has lifted more people out of poverty than any program. Some emphasize direct help, since growth can leave people behind for a long time. Economists broadly agree on a few points: education raises earnings, a strong job market is the best anti-poverty program, and how aid is designed matters, because a program that cuts off sharply when income rises can discourage work. How much to redistribute, and from whom, is a question of values that economics informs but cannot settle.

Everything you studied this year rests on one fact: scarcity. Wants are unlimited and resources are not, so every person, business and government must choose. Every choice has an opportunity cost, the next-best thing given up, and the honest way to think about any decision is to name that cost. A Saturday shift costs the game. A tariff on steel costs the machinery jobs. A dollar of tax spent on one program is a dollar not spent on another.

People respond to incentives, and most of what economics predicts follows from that. Raise the price of something and people buy less of it and make more of it; that is the law of demand and the law of supply. Put a ceiling under the price and you get a shortage; a floor over it and you get a surplus. Tax something and you get less of it, subsidize it and you get more. Whenever a policy surprises its designers, the usual reason is an incentive they did not see.

Markets coordinate millions of these choices through prices. A price is a signal that carries information nobody could gather on purpose: how much people want a thing and how hard it is to make. Where markets work, they push resources toward the uses people value most, and trade between people and between countries makes both sides better off. Where they fail, because of pollution, public goods, monopoly or missing information, government has a role, and that role has costs and limits of its own.

Finally, think at the margin and count everything. The question is rarely all or nothing; it is one more hour, one more unit, one more dollar, and whether its extra benefit beats its extra cost. Count the costs that are not on the price tag and the benefits that are not on the receipt. Keep sunk costs out of it. Measure the economy with GDP, the CPI and the unemployment rate, knowing what each one misses. These habits will not tell you what to value. They will tell you what your values cost.

Take a decision that faces many high school seniors: go to a four-year college, go to community college, or work full time. Start with numbers. Suppose a full-time job pays $32,000 a year. A public university costs $15,000 a year in tuition and fees after aid, for four years. The tuition is only part of the cost. The opportunity cost of four years in college includes the $32,000 a year not earned, which adds up to $128,000. Total cost of the college path, tuition plus forgone earnings, is roughly $188,000.

Now the benefit. Suppose college graduates in the field you want earn $55,000 to start instead of $32,000, a difference of $23,000 a year. At that gap, the $188,000 cost is recovered in about 8 years of work, and the gains keep coming for decades after. The numbers are examples, and they change with the field, the school and the person. But the structure is always the same: cost, including opportunity cost, against benefit over time.

Then trace the incentives and the trade-offs. Community college for two years cuts tuition sharply and lets a student keep a part-time job, lowering the opportunity cost. Working first and studying later trades money now for a smaller lifetime gain. Borrowing to pay tuition adds interest, and a loan must be repaid whether or not the degree is finished. A student who is unsure of finishing faces a very different calculation from one who is certain. There is no single right answer, only a right way to think.

The same method works on any policy question in this course. A proposed tariff: name who pays, who gains, what happens to prices and to retaliation, and put a number on the cost per job. A minimum wage increase: trace what employers do, what workers gain, and what economists on each side predict. A tax change: ask who bears it and what behavior it changes. When you can do that, and then say which trade-off you would accept and why, you are thinking like an economist.