But as central bank's appear to be running out of options, their moves to weaken their currencies have become increasingly unsuccessful.
The dollar fell to a 15-month low against the yen on Thursday, on track for its worst week against the yen since 2008.
The dollar fell to a 15-month low against the yen on Wednesday as investors packed into the safe-haven Japanese yen.
The dollar tumbled to a four-month low on Tuesday as growing fears of a global slowdown pushed investors to safe-haven currencies.
The yen surged by half a percent against the dollar as worry over Europe's banks drove capital to the safety currecny.
The dollar rebounded on Friday after data showed a pickup in U.S. wages, suggesting rates hikes are more likely to happen in 2016.
The dollar was on the defensive after a collapse in hopes of a further rise in U.S. interest rates this year drove its biggest daily fall.
The yen rose on Wednesday as weaker stock markets in Europe spurred investors to buy safe haven assets.
The U.S. dollar fell against the euro and yen on Tuesday after a drop in oil prices suggested U.S. inflation would stay low.
The U.S. dollar fell against a basket of major currencies on the view that the Fed would not be able to hike interest rates as quickly as forecast.
The dollar rose sharply on Friday, hitting a six-week high versus the yen.
The dollar hit a one-week low against the euro on Thursday after a plunge in U.S. durable goods orders.
Commodity-linked major currencies including the Australian and New Zealand dollars surged on Thursday as oil traded back above $33 a barrel.
The safe-haven yen and the low-yielding euro halted their rise on Tuesday, as stock markets and oil prices recovered.
The dollar edged down on Monday as renewed selling on oil markets drove investors into currencies often deemed less risky investments.
The dollar firmed Friday, boosted by expectations of monetary easing by in Europe and Japan, and by strong U.S. housing data.
The dollar turned negative against the euro on Thursday, reversing a morning rally.
The dollar fell to a more than one-year low against the Japanese yen as crude oil prices dropped near 13-year lows.
The dollar posted modest gains on Tuesday, as investor risk appetite improved on the back of rising oil prices and the expectation of further stimulus in China.
A recovery in stock markets helped the dollar gain ground against Europe's current safe havens of choice, the euro and the Swiss franc.