Americans are participating in the workforce at the lowest level in 35 years, according to government data released Friday, as lackluster job growth fails to offset the droves of people who have given up looking for work. According to the Labor Department, the economy added a disappointing 169,000 jobs in August. In addition, the government lowered its estimate of the number of jobs created in June and July by 74,000 positions.

The grinding pace of recovery has hollowed out the workforce. Government data showed that only 63.2 percent of working-age Americans have a job or are looking for one, the lowest proportion since 1978. Nearly 90 million people are now considered out of the labor force, up 1.7 million from August 2012.

There are demographic trends underlying the decline in the labor force. For much of the past generation, growing numbers of working women boosted its size, but that effect has leveled off. Meanwhile, the first baby boomers are reaching retirement age, and students are staying in school longer before looking for a job.