The combination of persistently high unemployment and low inflation has prompted some Fed officials, and outside critics, to question whether the asset purchases are worthwhile.

“With the benefits of quantitative easing essentially at zero, this equivocating action by the Fed is less about the economy and more about its unwillingness to begin the tapering that everyone knows must begin,” Representative Kevin Brady, a Texas Republican who is chairman of the congressional Joint Economic Committee, said in a statement.

Wednesday’s decision was supported by nine of the 10 voting members on the Fed’s policy-making committee. Esther L. George, the president of the Federal Reserve Bank of Kansas City, dissented as she has done at each meeting this year, repeating her concerns that the Fed’s campaign risks destabilizing financial markets and unleashing inflation.

Other critics, by contrast, draw the lesson that the Fed is being too cautious. Some contend the Fed should increase the volume of its asset purchases; some want the Fed to consider more radical measures, like explicitly targeting a temporary increase in inflation.

The Fed’s internal debate, however, has mostly been restricted to a narrow middle ground, pitting those arguing for more of the same against those pressing for just a little less.

After surprising Wall Street by deciding in September not to scale back their stimulus programs, Fed officials said this month that a resumption of that debate was likely to be postponed until December because the government shutdown had obscured their view of the economy. Temporary job losses during the shutdown are expected to blur the monthly unemployment reports for both October and November. The next clear snapshot of the job market will not be published until early January.

Ben S. Bernanke, the Fed chairman, said in 2010 that he had accepted a second term as Fed chairman in part to manage the Fed’s exit from its stimulus campaign. But he is scheduled to step down at the end of January, making it increasingly likely that the pullback will be directed by Janet Yellen, the Fed’s vice chairwoman and President Obama’s nominee to succeed Mr. Bernanke.