Here is one of the results of IGM Chicago’s Economic Experts Polls. Their panel of economic experts were selected to be a representative sample of economists. They represent economists’ actual distribution of political positions, genders, ages, and the like.
Not surprisingly, they come to a big consensus on free trade.
Foreign products sell because they can be produced more cheaply (they have the comparative advantage.) When their domestic competitors find something else to do, then two things are getting made instead of one! Protect domestic producers from foreign competition, then one thing gets made instead of two!
