President-elect Trump has promised to impose 25% tariffs on all goods imported from Canada and Mexico, and tariffs as high as 60% on goods coming from China on day one of his new administration. What will these protectionist policies accomplish?

WASHINGTON—President-elect Donald Trump pledged that soon after taking office he will slap steep tariffs on Mexico and Canada, two of America’s closest allies, as well as China, the clearest indication since his election victory that he plans to follow through on the tough campaign rhetoric that helped propel him to the White House.

Trump, who takes office on Jan. 20, said he would impose a 25% tariff on imports from Canada and Mexico until they clamped down on drugs, particularly fentanyl, and migrants crossing the border, in a move that would appear to violate a free-trade deal.