The decline in the labor force participation rate in the U.S. employment report appears to be driven by older-prime age workers -- the 45 to 54 cohort. That fell from 80.7 to 80.2 percent.

U.S. hiring rebounded in April and the unemployment rate dropped below 4 percent for the first time since 2000, while wage gains cooled by more than forecast in a sign that the labor market still isn’t tight enough to spur inflation.

Payrolls rose 164,000 after an upwardly revised 135,000 advance, Labor Department figures showed Friday.

Average hourly earnings increased 0.1 percent from the prior month and 2.6 percent from a year earlier, both less than projected. The jobless rate, derived from a separate survey of households, fell to 3.9 percent, the lowest since December 2000, after six months at 4.1 percent.