There are no two ways about it: 2017 has been a brutal year for US dollar bulls.

As of this writing, the world’s reserve currency has fallen against every one of its major rivals on the year, losing a staggering 12% against the euro and over 8% versus the British pound. Incredibly, this move has occurred despite the Federal Reserve being arguably the most hawkish of the major central banks, hiking interest rates three times while many of its rivals remained on hold.

So what drove the dollar lower throughout the year? The same thing that always moves markets: an imbalance between buyers and sellers.

It seems like a lifetime ago, but recall that as the calendar flipped to 2017, hopes were running high that “Businessman President” Donald Trump would unlock the growth potential of the US economy through a combination of cutting taxes and reducing burdensome regulations. With the help of a Republican-controlled Senate and House of Representatives, traders’ expectations for a pro-business agenda spawned a surge in the greenback and US stocks (the so-called “Trump Trade”).

This view was reflected in the CFTC’s Commitment of Trader (COT) data, which showed that speculative futures traders were holding net long positions in the US Dollar Index to the tune of over 54,000 contracts at the start of the 2017, essentially the highest net long position in over a year. As President Trump struggled to enact his legislative agenda and the US economy encountered some hurdles, the optimism bubble gradually deflated, and the US dollar fell consistently throughout the first three quarters of the year.

Now, we’re presented with the mirror image scenario from the start of last year: expectations are low that Republicans on Capitol Hill will be able to get any legislation signed, and dollar index traders are now positioned net short over 4,000 contracts, the most bearish reading since mid-2014. In other words, the pendulum of market sentiment has shifted from extreme bullishness with high expectations to extreme bearishness with low expectations, potentially setting the dollar up for a far better year in 2018 than 2017.