As everybody knows from Econ 101, protective tariffs are harmful for the country that imposes them. A protective tariff is a tax on imports that is so high as to make all imports fall to zero.
But there is an argument why a low tariff may be better than no tariff at all. The reason is that a large country (large compared to its trading partners) faces an upward-sloping supply curve for its imports such that a fall in import demand lowers the world-market price of imported goods. Hence, part of the cost of the increased tariff would fall on the rest of the world due to lower export prices (a fall in the terms of trade) while the country that imposed the tariff might win overall.
Whatever the theoretical merits and demerits of this argument, recent experience with tariff increases in the US (aka Trump’s Trade War) provides powerful evidence against it.
In a newly released paper, Amiti, Redding and Weinstein show that the tariffs imposed last year by the Trump administration had two main effects:
1) US prices of imported goods rose one-for-one with increases in tariff rates.
2) Import demand decreased substantially with an estimated price elasticity of 6 (i.e. 6 percent lower imports for every 1 percent of higher tariffs).
As a consequence of these two results the paper estimates the welfare costs of the Trade War to be about 6.9 billion dollars. While that is not a huge number compared to the total size of the US economy, keep in mind that we’re only talking about a marginal change of the average tariffs from 1.5 to about 3.25 percent. And remember that the welfare costs rise with the square of the applied tariff rate. So should tariffs go up more in the future, the welfare costs will be much bigger.
I regard this as decisive evidence that the optimum tariff is indeed zero. Note that finding No. 1 implies that American consumers are paying the full cost of the tariff increase, with no terms-of-trade effect on the rest of the world. If even the largest economy in the world cannot improve their terms of trade by increasing tariffs, then smaller economies have no hope of doing so either. Raising tariffs is indeed shooting yourself in the foot.
Moreover, this paper is also a triumph for simple textbook economics. The results of Trump’s tariffs are exactly what one would expect from the kind of supply-and-demand model taught in Econ 101. As Tyler Cowen points out, the complete pass-through of tariffs to consumer prices also implies that monopoly power is not a big issue in these markets. It’s good to know that the much-maligned perfect competition partial equilibrium models still gets some important things right.