Just how high can the dollar rise?

The U.S. dollar index, which tracks the dollar’s strength against a basket of six currencies but is primarily weighted toward the euro touched a 12-year high on Friday. Even more impressive than the level has been the pace—according to Steven Englander of CitiFX, the dollar’s rally over the past eight months has been its fastest in at least 40 years.

But far from being ready to take profits, many dollar bulls continue to say that it’s still full-steam ahead for the greenback.

With little resistance in sight on the chart, “we have another 10 percent to go,” according to Todd Gordon of TradingAnalysis.com.

In the options market, traders certainly appear to be betting on further dollar gains—and euro losses. In one particularly big trade in the prior week, someone bought a huge number of bearish put spreads on the ETF tracking the euro, the FXE.

“The price they traded suggests at least a 25 percent probability that we’re at parity by year end here,” said Stacey Gilbert, head of derivatives strategy with Susquehanna, referring to the state in which each euro costs $ 1. Currently near $ 1.05, the euro neared $ 1.40 in April.

The catalyst for the huge move is clear. The Federal Reserve is preparing to raise short-term rates, which will make it more attractive to hold dollars. Meanwhile, the European Central Bank has just commenced a currency-weakening quantitative easing program. And all this as the U.S. economy far outperforms Europe.