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.

The economy added a disappointing 169,000 jobs in August, according to the Labor Department. 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.

“We just don’t see this consistent, strong job market that’s really going to entice people to go back into it,” said Michael Evangelist, policy analyst at the National Employment Law Project. “You don’t want people falling out of the labor force where they’re not able to contribute and not able to find work.”

Carol Petty, 54, is among those hanging in the balance. She lost her job as a paralegal in Nevada last summer and has struggled to find work since. Petty moved to California to be near her family and hoped she would find a better job market. She sends out as many as 10 resumes a week and knows she is unlikely to find another position that pays her old salary of $55,100 a year.

She said others in her position have given up seeking work. The question for Petty — and the broader economy — is how long people like her will be able to hold on. “I’m just so stubborn,” she said. “I will do anything.”

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 wave of baby boomers is reaching retirement age, while younger workers are staying in school longer before looking for their first job.

Economists believe those shifts cannot fully explain the size of the decline. Research released this spring by two Federal Reserve economists showed that states with the largest drops in unemployment also had bigger declines in the labor force, suggesting the slow pace of recovery is the culprit.

Before the recession, the government studied population changes and forecast that the participation rate would dip by 0.3 percentage points from 2007 to 2012, according to the paper. Instead, it fell by 2.5 percentage points. Economists had hoped that the recovery would pick up steam during the second half of this year.