The dollar's sell-off raises concerns that investors are losing trust in the U.S.

Since mid-January, the dollar has fallen 9% against a basket of currencies, a rare and steep decline, to its lowest level in three years — a drop that raises concerns investors may be losing confidence in the U.S.

Currencies rise and fall all the time because of inflation fears, central bank moves and other factors. But economists worry that the recent drop in the dollar is so dramatic that it reflects deeper investment concerns as President Donald Trump tries to reshape global trade.

The dollar's dominance in cross-border trade and as a safe haven has been nurtured by administrations of both parties for decades because it helps keep U.S. borrowing costs down and allows Washington to project power abroad — enormous advantages that could possibly disappear if faith in the U.S. was damaged.