[_dps]

> No economist has ever claimed that global trade is Pareto-optimal inside nations.

This is an important point, and I think plays into the question about tariffs (which, to be clear, I think are probably net negative).

The conventional argument is that free trade is a Kaldor Hicks [0] improvement, not a Pareto improvement. KH means that the sum of benefits and costs is positive, and it would be possible (in principle) to tax the beneficiaries and pay off the people harmed and create a synthetic Pareto outcome.

You could view tariffs as a clumsy attempt to apply the Kaldor-Hicks concept. I personally think there are much better ways, but I think the argument is at least plausible.

[0] https://en.wikipedia.org/wiki/Kaldor%E2%80%93Hicks_efficienc...