The Labor Department says just 16 percent of eligible workers took time off last year under the Family and Medical Leave Act to recover from an illness, care for a new child or tend to a sick relative.
The data comes from a government survey issued on the law's 20th anniversary. Labor officials say it shows the law is helping millions of workers cope with family hardships with little disruption to employers.
The law allows eligible workers up to 12 weeks of unpaid leave without fear of losing their jobs.
Since it took effect, workers have taken leave more than 100 million times. Last year, about 57 percent went on leave for an illness. Another 22 percent took leave for child care and 19 percent cared for a sick relative.