As college students across the country begin their final exams, we are reminded of the unfortunate reality that much of what we learn in school or other parts of life will eventually be forgotten. Usually, this is more of a nuisance than a problem. A failure to recall the finer points of Shakespearean literature is unlikely to trouble most accountants, nor is a marketing specialist apt to lose sleep over the lost ability to define the Pythagorean Theorem. It’s a bigger problem, however, when the Secretary of Commerce forgets some basic lessons of international trade.

Appearing at an Atlantic Council event earlier this week, Commerce Secretary Wilbur Ross argued that the Korea-U.S. Free Trade Agreement (KORUS) should address the U.S. trade in goods deficit with South Korea. Despite the fact that economists generally agree that the trade deficit is not a good indicator of a country’s economic performance—or as our colleague Dan Ikenson argues, is not a problem to solve—Secretary Ross thinks otherwise. In the context of president Trump’s recent visit to Asia, he stated the following:

President Trump…underscored the need to rebalance the KORUS free trade agreement to reduce the substantial trade deficit that we have with Korea. That deficit has nearly tripled to $27.7 billion since KORUS went into effect. Among the most important reasons for the increased deficit has been the imbalance between automotive imports and exports. Our automotive imports from Korea are almost nine times our exports of autos to them. And remarkable as it may sound, we export to Korea more dollars’ worth of corn and beef combined, than we do cars—seems strange for an industrialized economy.

The solution he offered to this “problem” was for South Korea to agree to purchase more liquefied natural gas, petroleum, food products, machinery and industrial equipment from the United States instead of other countries.

There are two basic things Secretary Ross gets wrong with this line of reasoning. First, he misunderstands the one true and nontrivial principle in the social sciences, which is Ricardo’s theory of comparative advantage. Second, by focusing only on goods—and cars in particular—he ignores the diversity of the U.S. economy, and some of its greatest strengths, such as the services industry. We address both in turn.

David Ricardo clearly explained the theory of comparative advantage in On the Principles of Political Economy and Taxation 200 years ago. He stated:

If Portugal had no commercial connexion with other countries, instead of employing a great part of her capital and industry in the production of wines, with which she purchases for her own use the cloth and hardware of other countries, she would be obliged to devote a part of that capital to the manufacture of those commodities, which she would thus obtain probably inferior in quality as well as quantity.

The quantity of wine which she shall give in exchange for the cloth of England, is not determined by the respective quantities of labour devoted to the production of each, as it would be, if both commodities were manufactured in England, or both in Portugal.

England may be so circumstanced, that to produce the cloth may require the labour of 100 men for one year; and if she attempted to make the wine, it might require the labour of 120 men for the same time. England would therefore find it her interest to import wine, and to purchase it by the exportation of cloth.

To produce the wine in Portugal, might require only the labour of 80 men for one year, and to produce the cloth in the same country, might require the labour of 90 men for the same time. It would therefore be advantageous for her to export wine in exchange for cloth. This exchange might even take place, notwithstanding that the commodity imported by Portugal could be produced there with less labour than in England. Though she could make the cloth with the labour of 90 men, she would import it from a country where it required the labour of 100 men to produce it, because it would be advantageous to her rather to employ her capital in the production of wine, for which she would obtain more cloth from England, than she could produce by diverting a portion of her capital from the cultivation of vines to the manufacture of cloth (para. 7.13-7.16).

This example highlights an important element of comparative advantage. First, even if one country is the best at everything (in other words, has an absolute advantage), it is still better served by focusing on what it produces best, and importing the remaining items. Why? Because an absolute advantage does not necessarily equal a comparative advantage, as the latter is based on the opportunity cost of making one thing over another. For instance, if planning a birthday party with a friend, and you’re better at both baking cakes and writing nice invitations but only slightly better at the invitations, it makes more sense for you to bake the cake and for your friend to send out the invites than for you to do both. It not only is more efficient, but it also spares up the time you would have spent writing those invitations to focus on making an even better cake. Essentially, comparative advantage allows for greater investment in the thing you are good at, and in turn, makes you better at it over time.

This logic is easily applied to the bilateral trade relationship between the United States and South Korea. Endowed with vast amounts of land ideally suited both for cattle grazing and growing of corn, the United States enjoys a considerable comparative advantage in such products and is the world’s largest producer of both. Lacking such geographic advantages but possessing a highly-skilled workforce and some of the world’s leading manufacturing firms, South Koreans instead specialize in the production of cars. By focusing on what each country does best, and then engaging in trade, the citizens of both countries are made better off. Rather than building cars, Iowa corn farmers raise crops, harvest them, and then send them to foreign lands where in exchange they receive cars and other needed goods. To force South Korean autoworkers to grow their own corn or Iowa farmers to build their own cars would be to live in a less prosperous world.

Also overlooked by Secretary Ross is that a country as vast and economically developed as the United States is able to enjoy comparative advantages across multiple sectors and industries. In addition to being an agricultural juggernaut, the United States is—perhaps contra the popular narrative—a manufacturing powerhouse with output near record highs. While the United States does indeed send large amounts of beef, corn, and other agricultural products to South Korea—$6.2 billion worth in 2016—these are dwarfed by its manufacturing exports.  Indeed, one category of manufacturing exports alone, machinery, saw exports ($6.1 billion) nearly equal to agricultural products in their entirety. The United States exported another $5.3 billion worth of electrical machinery, $5.2 billion in aircraft, and $2.9 billion worth of optical and medical instruments, in addition to vehicle sales of $2.2 billion.

Beyond its massive agricultural and manufacturing sectors, the United States—like most advanced economies—is also increasingly oriented towards the production of services where it possesses considerable expertise. Not mentioned by the Commerce Secretary is that the United States exported $21.6 billion in services to South Korea in 2016 and was left with a trade surplus in this sector of $10.7 billion.

Unlike the goods trade deficit, Secretary Ross has made no indication that he believes this particular trade surplus to be a problem or that he intends to pressure Americans into purchasing additional South Korean services to achieve balance. Nor should he. Rather, the citizens of both the United States and South Korea should be left to their own devices to purchase the products and services they desire and trade as they see fit with minimal interference. Instead of bemoaning a goods trade deficit that is more statistical quirk than indicator of economic vitality, or puzzling over why the United States does not export more of a particular good, Ross would do better to spend his time removing the remaining barriers to trade between the United States and South Korea and allowing the miracle of comparative advantage to work its magic.