Inflation has been running above the central bank's 2% target for more than five years. Some Fed officials have been arguing since April that it's time to raise interest rates to address that.

Most of the central bank's decision makers, though, showed patience-up to a point. Through the spring and summer, they were willing to wait and see whether, despite elevated energy prices, broader inflation trends might cool enough to let the Fed stay on pause. Relatively benign inflation data in June and July looked promising enough to support that plan.

Investors have been antsy, however. Many felt, after new Fed Chairman Kevin Warsh's July press conference, that he hadn't been clear enough about his eventual plans to address inflation if it didn't decline on its own. That sent long-term Treasury yields higher. With that anxiety hanging over markets, Warsh took a stronger anti-inflation tone in a major speech in late August, reiterating a pledge to corral inflation if it didn't show more cooling.

Last week, the latest inflation data didn't cooperate-likely leaving the inflation metric the Fed tracks in the mid-3% range in August. Now, investors widely believe that given stubborn inflation data-and despite pressure from the Trump administration to keep rates low-Warsh and his colleagues have left themselves little choice but to follow through on their words with a rate increase.