U.S. dollar is currently trading at lowest level in nearly 3 years.

The U.S. dollar is cooling off recently since reaching new highs at the start of the year.

Though it rose in the weeks following President Trump's election victory last November, the greenback has steadily fallen this year.

It's now down to its lowest level since January 2015. Since January 3, the first trading day, the dollar is down 11%.

It's down nearly 17% against the Mexican peso this year, a reversal of fortunes after Trump's campaign threats caused the peso to plunge. It's also down 12% against the euro and 7% against the pound.

Investors were optimistic late last year that the Trump administration could cut taxes, pass an infrastructure bill and clear out financial regulations. But they're losing confidence.

"There was a lot built into it at the beginning of the year - none of that's materialized," says Kathy Jones, chief fixed income strategist at Charles Schwab. "No infrastructure spending, no tax cuts...it really has flipped the script from where we were at the beginning of the year until now."

Other factors have contributed to the dollar's decline this year, but "a lot of it" is linked to Wall Street's disappointment with the progress of Trump's agenda, Jones adds.

What else is hurting the dollar's value:

- Dimming hopes of another rate hike this year at the Federal Reserve

- Europe's economy is picking up momentum after years of playing catch up to the U.S. economy

- European political risks, such as the French election and the Brexit vote, are now in the rear view mirror, boosting the euro and the British pound against the dollar. A litany of other factors influences the dollar's value too.

But above all, the dollar's surge rode on investors' optimism for tax reform and new roads, bridges and rails. Treasury Secretary Steven Mnuchin said Tuesday that tax reform could still happen this year, and the dollar is up a notch this week.