It took more than a decade for Paul Volcker and Alan Greenspan to wring persistently high inflation from the U.S. economy. Federal Reserve officials now may need at least half that time to bring too-low inflation back to their target.

Fed Chair Janet Yellen, Vice Chairman Stanley Fischer and most other U.S. central bankers remain confident further improvement in the labor market will gradually lift prices to the central bank’s 2 percent objective. That’s become a divisive assumption as the Federal Open Market Committee heads into a meeting later this month.

The August employment report released Friday will sharpen the debate. The figures showed a monthly net gain of 151,000 jobs, an unemployment rate holding at 4.9 percent and a slowdown in wage growth.

There’s ammunition in the latest data for officials who want to delay a rate increase as they look for signs of continued tightening in the job market. A critical component in Fed officials’ forecast is a rise in wages that boosts demand and drives prices higher.

“Nobody understands the inflation process, including the Fed,” said Torsten Slok, chief international economist at Deutsche Bank in New York. “When we are near full employment, why has inflation been so incredibly well-behaved?”

After the report, traders trimmed their bets on a rate hike at the Sept. 20-21 FOMC meeting to a roughly 14 percent chance, according to federal funds futures contracts.

The mystery of weak wage growth is troubling, for the short run and the longer-term. If Yellen and the FOMC majority are wrong, inflation could remain stuck below their target, setting the economy up for lower rates of inflation in the next downturn.

“The risk is that when the next crisis hits, you fall from 1.5 percent inflation to 0.5 percent inflation, and then to deflation in the next recession after that,” said Ethan Harris, head of global economics research at Bank of America in New York. “You are going down a slippery slope.”

What’s more, Harris said, very low rates of inflation can lead to higher rates of unemployment in a downturn. Rather than cut wages as their prices fall, companies tend to cut workers instead.

The jobless rate has plunged from 8 percent at the start of 2013. Inflation over that time was steady around an annual rate of change of 1.6 percent, according to an underlying measure of inflation tracked by the Dallas Fed, leading many economists to wonder whether parameters in traditional inflation models have shifted.

“Slack doesn’t matter” as much as it once did, said Laurence Meyer, who as a Fed governor from 1996 to 2002 was one of central bank’s biggest proponents of the Phillips Curve, a description of the tradeoff between unemployment and inflation.

Maribel Martinez, accompanied by her attorney Sanford Rubenstein, left, and a translator, speaks at a news conference at her attorney’s office, in the Brooklyn borough of New York, Thursday, Sept. 1, 2016. Martinez says she hasn’t stopped crying since JetBlue airlines mistook her son for another child and flew him to the wrong city. (AP Photo/Richard Drew)

Richard Drew