CAMBRIDGE, Mass. — THE Federal Reserve is pursuing a very risky monetary policy. Its leaders — the departing chairman, Ben S. Bernanke, and the vice chairwoman, Janet L. Yellen, whom President Obama has nominated to succeed him — are correct that the American economy needs more stimulus, and they believe that the central bank, because of political paralysis, is the only game in town. But if Congress and the Obama administration could agree on a fiscal stimulus that goes beyond a short-term budget deal, the Fed would not have to take such risks.

The Fed’s strategy has been to stimulate the economy by driving down long-term interest rates by amassing long-term bonds and pledging to keep short-term rates near zero. A result has been to increase home and stock prices and, by lifting household wealth, encourage consumer spending.

But the magnitude of the effect has been too small to raise economic growth to a healthy rate. Home building has increased rapidly, but from such a low level that its contribution to gross domestic product has been very small. And the increase in total consumer spending has slowed, despite the soaring stock market.

The net result is that the economy has been growing at an annual rate of less than 2 percent. (The latest estimate, that the economy grew at an annualized rate of 3.6 percent in the third quarter, overstates the strength of demand because half of that increase was just because of inventory accumulation.) Weak growth has also meant weak employment gains. The decline in unemployment, to 7 percent, as announced on Friday, has largely reflected the decreasing number of people looking for work. Total private-sector employment is actually less than it was six years ago.