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The Federal Reserve declined to raise its benchmark federal funds rate on Thursday, saying that uncertainty abroad, volatility in financial markets and stubbornly low inflation persuaded members that the U.S. economy is not yet growing strongly enough to merit a light tap on the brakes.

Speaking at a news conference shortly after the decision was announced, Fed Chairman Janet Yellen said that most members of the Fed's Open Market Committee remain persuaded that a rate hike will be appropriate before the end of the year.

The committee announced the decision at the conclusion of a two-day meeting in Washington to assess the state of the nation’s economy.

The vote to keep rates in the zero to 0.25 percent range was 9-1. Member Jeffrey Lacker had wanted to raise the rate by a quarter point — a move seen on Wall Street as a virtual lock just a month ago until markets revolted. Stocks headed up after the announcement, with the Dow Jones industrial average gaining more than 170 points in the first 40 minutes.

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Though giving a nod to an improving economy, with expectations slightly higher for gross domestic product and lower for the unemployment rate than three months ago, the Fed said low levels of inflation remain a problem.

"The committee anticipates that it will be appropriate to raise the target range for the federal funds rate when it has seen some further improvement in the labor market and is reasonably confident that inflation will move back to its 2 percent objective over the medium term," the committee's post-meeting statement said.

In its economic projections, Fed members showed misgivings despite improvements in a number of areas.

The Fed has what is known as a dual mandate — price stability and maximum employment. The unemployment rate, currently at 5.1 percent, is well below the Fed's initial 6.5 percent benchmark for raising rates, but inflation, at least by the FOMC's favored gauges, has remained tame.

The "central tendency" for headline inflation, as gauged by the personal consumption expenditures index, is now at just 0.3 percent to 0.5 percent, down from an already-anemic 0.6 percent to 0.8 percent in June. Projections for core inflation, which excludes energy and food, held steady at 1.3 percent to 1.4 percent, well below the Fed's 2 percent target.

Concerns over the slow pace of inflation seemed to carry the day, as members adjusted their expectations for the pace of future rate increases.

The rate has been in the zero to 0.25 percent range since Dec. 16, 2008, when the committee cut it to help the U.S. economy pull out of a steep recession triggered by the housing crash.

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The committee adjusts the federal funds rate — the interest rate that banks charge other banks on overnight loans — to influence the supply of money, control inflation and keep the economy stabilized.

A rate change would have affected consumers in more direct ways, too, inflating payments for certain financial products and services.