The New York Stock Exchange is bathed in holiday light in New York on Dec. 11. (AP Photo/Mark Lennihan, File)
Powell also acknowledged that the Fed's decisions are getting trickier because they need to be based on the most up-to-date figures on jobs, inflation, and economic growth. For the last three years the Fed told investors weeks in advance that it was almost certain to increase rates. But things are less certain now, and the market hates uncertainty.
Treasury Secretary Steven Mnuchin said the market's reaction to the Fed was "completely overblown."