Early on in my introductory economics course I warn my students always to beware of various logical fallacies, none of which is more prone to sow confusion than the fallacy of composition. This fallacy is committed whenever someone concludes that that which is true for a part of the group is necessarily true for all of the group. The classic example is standing up in a stadium to get a better view of the game. If one or a small number of people stand up, these folks do indeed enjoy a better view. But obviously it’s mistaken to conclude that “therefore, if everyone stands up, everyone will get a better view.”

Protectionists commit the fallacy of composition whenever they point – as they incessantly do – to particular firms that get more sales, and to workers who keep particular jobs, as a result of tariffs and other trade restrictions. No serious student of trade has ever denied that protectionism can protect particular firms and workers who are awarded protection. But nor has any serious student of trade failed to see that the protection enjoyed by the few comes at the larger expense of the many.

The example of standing up in the stadium is useful for exposing some of the significant negative consequences of protectionism – consequences stubbornly ignored by protectionists.

The first of these typically overlooked consequences is that, just as someone who stands up in a stadium worsens the view of several people sitting behind him, protection granted to a few producers worsens the economic prospects of more than a few fellow citizens. The most obvious victims are final consumers of the protected goods. These consumers suffer by having to pay higher prices and perhaps also enduring lower quality. Their standard of living falls.

Consumers aren’t alone in their victimization. Domestic producers who use imports as inputs in their own operations also suffer. With their costs raised by protective measures, these producers must raise their prices and scale back production. And as they scale back production they lay off some of their workers. These workers eventually find other jobs, but because protection diverts capital away from more-efficient to less-efficient industries, the new jobs these workers find will generally be less productive and, hence, pay lower wages.

Importantly, among the domestic producers who are harmed by protection are exporters. The Lerner symmetry theorem explains that changes in imports change exports in the same direction. It’s not excessive simplification, for example, to note that if we Americans buy fewer imports, foreigners receive fewer US dollars. Having fewer US dollars, foreigners buy fewer US exports.

But even many firms that don’t export are, through the Lerner symmetry theorem, harmed by protectionism. In his original formulation of his theorem, Abba Lerner assumed “the absence … of capital movements between the countries,” that is, no international investment. Obviously, though, international investment does occur and, since the Bretton Woods system collapsed in the early 1970s, it occurs on a large scale. (Among the tools the Bretton Woods system used to stabilize exchange rates was a restriction of international capital flows.) Therefore, when reduced American imports shrink the flow of dollars to foreigners, not only do foreigners purchase fewer American exports, they also invest less in America. It’s the same as would occur if your income fell: you would reduce both your consumption and your investment.

This reduced flow of capital into America raises real interest rates and chokes off some investment that would otherwise occur. And so even many firms that neither export nor use imports as inputs will suffer as a consequence of protectionism through the shrinkage of domestic investment.

A second way in which the standing-up-in-the-stadium analogy illuminates some problems with protectionism is this: Just as it’s foolish to conclude that, because a few people in the stadium are made better off by standing up, everyone in the stadium would be made better off if everyone stands up, it’s foolish to conclude that, because one or a handful of producers are made better off by being awarded protection from imports, everyone in the country would be made better off if everyone received such protection.

The analogy, as so far stated, isn’t perfect. As a practical matter, across-the-board protectionist measures (such as President-elect Trump’s proposed across-the-board tariffs) will hit some domestic producers harder than they hit others. Across-the-board protectionism, therefore, can still wind up being a benefit to some producers. To return to the analogy, because, as a practical matter, some people in the stadium have longer legs than others, if everyone in the stadium stands up, individuals with especially long legs will nevertheless have a better view than they would have with everyone sitting down.

But this detail does nothing to dilute the core conclusion, which is that across-the-board protectionism will harm most people, both in their capacity as workers and producers. That is, while it’s possible that tariffs on a handful of imports will help all protected industries even as they impose net harm on the economy as a whole, it’s not possible that across-the-board protectionism will help all of the ‘protected’ industries.

This conclusion rests, in part, on the practical reality that some domestic producers will indeed benefit from across-the-board protection. The prices these producers will charge will rise relative to the prices charged by other producers, and the outputs of these fortunate producers will expand. But of course this fact means that the outputs of other domestic producers will shrink as the domestic producers who expand draw resources away from other producers. And because the producers whose outputs expand are unlikely to be those with comparative advantages at producing more output, across-the-board tariffs will shift capital and labor from more- to less-productive uses, inflicting domestic economic damage that, if not completely across-the-board, is quite widespread.

There is no saving the case that protectionism is a means of enriching the people of a country as a whole. This case is as illogical as is the conclusion that everyone at the big game will get a better view of the field of play if everyone stands up.