Watching anticipation of a rate cut has been like watching high-speed volleys during a tight tennis match. But the speculation of markets part is over; the central bank's Federal Open Market Committee has made its decision. The Federal Reserve is cutting the benchmark federal funds rate by 50 basis points. That makes the federal funds rate a range of 4.75% to 5%.

"The Committee has gained greater confidence that inflation is moving sustainably toward 2 percent, and judges that the risks to achieving its employment and inflation goals are roughly in balance," the central bank wrote. "The economic outlook is uncertain, and the Committee is attentive to the risks to both sides of its dual mandate."

Trying to predict the outcome has become a new sport, with the 30-day federal funds futures market fluctuating for weeks as to chances of a 25- or 50-basis-point cut, according to CME Group's FedWatch. On August 16 it was 75% to 25% for the former; 86% to 14% on September 11; 36% to 64% yesterday; and 45% to 55% at around 1 p.m. today. That last was down from 31% to 69% this morning, according to LPL Financial.