President Donald Trump revealed his most sweeping economic measure yet Thursday, announcing reciprocal tariffs that could come as soon as this spring, which Trump argues would level the playing field in global trade—though economists project they would increase inflation this year.

Since the 1960s, tariffs — or import taxes — have emerged from negotiations between dozens of countries. Trump wants to seize the process. “Obviously, it disrupts the way that things have been done for a very long time,

Trump spoke to reporters from the Oval Office about his decision, saying it was an “amazing day.” When asked if prices would rise as a result of the tariffs, he said that they “could go up somewhat” at first, but then “prices will also go down.”