Inflation, minus food and energy, remains low at 1.2 percent by the Fed's preferred measure.
Job vacancies rose the most in April in data going back to December 2000.
Second, Fed Governor Lael Brainard cited the research in a June 2 speech where she made the case that "there are reasons to think that the natural rate may have declined over the past few years such that a gap remains between the unemployment rate and its natural rate."
Even if Fed officials do raise the benchmark lending rate in September, as about half the economists in a Bloomberg News survey this month expect, the research suggests the pace of tightening will be slow.
"It could mean that one percentage point of tightening per year is too steep in a world where" the rate of full employment is 4.25 percent, Gapen said.For more on the global economy, check out Benchmark: