Economists have given Federal Reserve Chair Janet Yellen amission for next week's press conference: Explain what “gradual”means.

The Federal Open Market Committee in September projected aninterest rate policy path that, including December, averages fourinterest rate hikes a year through the end of 2018. That's half thepace of the last tightening campaign, when rates were raised by aquarter point every meeting from June 2004 until peaking two yearslater at 5.25 percent.

Sixty-four percent of economists surveyed by Bloomberg News fromDec. 8 to Dec. 10 said the quarterly forecasts that officials willpublish Wednesday will show a slower path of increases than theirSeptember estimates. That's more in line with financial marketswhere prices on futures contracts for three-monthEurodollars—dollar deposits held at banks outside the U.S.—indicateabout two increases in 2016.

“There are some pretty widely varying views on whether the Fedis ahead or behind the curve and whether inflation is going to pickup very quickly,” said Michael Hanson, senior economist at Bank ofAmerica Corp. in New York.

Almost all of the 91 economists in Bloomberg News' separatemonthly survey see the Fed hiking by a quarter point, ending aseven-year era of near-zero rates.

Assuming the Fed raises rates on Wednesday, the second rate hikewould likely come in March, according the highest averageprobability assigned by the 45 economists surveyed.

Yellen told the congressional Joint Economic Committee Dec. 3that the “gradual” pace of interest rate increases was linked toher assumption that the so-called neutral rate—which keeps supplyand demand in balance in the economy—is low just now.

“It is a factor that leads us to believe that even when we startraising rates, that those rate increases will be gradual,” Yellensaid in response to a question at the hearing.

The neutral, or equilibrium, rate changes through time, and Fedofficials in September estimated that in the long run it willsettle at around 3.5 percent, or 1.5 percent in real termssubtracting for 2 percent inflation, which is the Fed's goal.

Economists in the survey are more optimistic, with their medianestimate showing the equilibrium real interest rate at 2 percent.Even so, they only expect the nominal interest rate to peak in thiscycle at 3.25 percent, according to the median.

“The Fed has spent this entire year telling us they are datadependent,” said Rajeev Dhawan, director of the economicforecasting center at Georgia State University in Atlanta. “And thesecond thing they are telling us is the natural rate of interest islower. These two things are being digested.”

For Dhawan, “gradual” means the Fed will raise the benchmarkrate a second time in March and then do nothing until Decemberafter the U.S. presidential election. He sees the next round ofrate hikes bringing the policy rate to 2 percent by the end of2017.

Another component of Yellen's gradual tightening strategy isabout when they will begin reducing the size of their $4.5 trillionbalance sheet. Some 62 percent of economists in the survey saidthat won't happen until 2017 or later.

Economists also had disparate views of inflation. Some 62percent don't expect the Fed's preferred inflation index, thepersonal consumption expenditures price index, or PCE, to achieve athird consecutive month of 2 percent or higher readings until 2017or later.

With the unemployment rate at 5 percent in November, just abovethe Fed's 4.9 percent definition of full employment, inflationperformance could be the central theme driving the rate-hikepace.

Michael Pond, head of global inflation strategy at BarclaysCapital Inc. in New York, said that the PCE's lower weighting forshelter and different measurement of medical costs versus theconsumer price index, and “continued weakness in core goods prices”means the index won't start hitting the 2 percent mark until thethird quarter of 2017.

That underwrites the firm's gradual pace estimates on interestrates. Barclays forecasts the benchmark lending rate will be in arange of 1 percent to 1.25 percent at the end of 2016, and a rangeof 1.75 percent to 2 percent at the end 2017, or zero ininflation-adjusted terms.

“We expect the Fed to be gradual in raising interest ratesbecause inflation pressures and expectations are low and there isconsiderable uncertainty around the level of the neutral real fedfunds rate,” Pond said.

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