This is how the unemployment rate drops...fewer people in the labor force.

Hiring in U.S. Kicks Into Higher Gear as Unemployment Plunges to 6.3%

"The drop in the unemployment rate from March’s 6.7 percent came as the agency’s survey of households showed the labor forceshrank by more the 800,000 in April. The so-called participation rate, which indicates the share of working-age people in the labor force, decreased to 62.8 percent, matching the lowest level since 1978, from 63.2 percent a month earlier."