President Donald J. Trump’s new tariffs could generate trillions of dollars in new federal government revenue over a decade, but the net gain would be reduced by the measures’ damaging effects on the US economy and the other economies’ likely retaliation, write Warwick J. McKibbin and Geoffrey Shutrim. They find that increasing universal US tariffs by 10, 15, or 20 percentage points would result in lower US GDP, employment, and real wages than otherwise.