WASHINGTON — Investors have concluded that the Federal Reserve will announce new measures to promote economic growth after a meeting of its policy-making committee ends Wednesday. Long-term interest rates have moved as if the Fed had already spoken.

The central bank is often described as facing the choice of whether to do more to improve the economy. But the anticipatory behavior of investors means the Fed really faces a slightly different choice, one it has confronted often in recent years: whether to risk doing less than expected.   Read more