– Even as the nation enjoys a historically low jobless rate and downtown Detroit booms with thousands of new workers and dozens of new projects, the long-term lack of work opportunities for Detroiters threatens to hold back the city for years to come.

Almost half of Detroit's working-age residents aren't even looking for a job — at 53.4 percent, it's the lowest workforce participation rate in the nation and a symptom of poverty and poor educational attainment.

Tyrone Burks puts a human face on some very bleak statistics.

Burks, 37, spent 10 years in a state prison for a sexual misconduct conviction. Released in 2013, he has worked temp jobs since, but struggles to find better full-time work.

But his obstacles only begin with his incarceration history. Having dropped out of high school, Burks is undereducated. While he completed his General Educational Development (GED) certification in prison, the rough equivalent of a diploma, many of the jobs available in Detroit require more education.

He recently finished pre-apprenticeship training to be an electrician at the Randolph Career and Technical Center in Detroit. But the sort of skilled trades jobs he's looking for generally want an even higher level of training and experience.

Transportation also is an obstacle. Burks doesn't have a car and hasn't been able to get his driver's license back because he owes traffic fines and penalties. His experiences are all too common for some 3,300 Wayne County residents returning to the community from prison each year. Of those citizens, 70 percent are still unemployed three years after their release, said Jeff Donofrio, the director of Detroit's workforce development office in Mayor Mike Duggan's administration.

Even after years of attacking joblessness, it remains far and away the key challenge holding back Detroit's full recovery. And past incarceration is only one part of the complex problem.

Failure to finish high school makes a major difference. The poverty rate among Detroit residents who fail to finish high school was 52.1 percent in the latest government data; the poverty rate for Detroiters with a bachelor's degree was 12.6 percent.

And marital status contributes, too. Among women participating in the workforce, the unemployment rate with a spouse present was 10.8 percent, but 23.1 percent for single moms. Everything from a lack of a car to unaffordable housing can make it harder to find or keep a job.

The city's official unemployment rate stood at 7.4 percent in April, well above the Michigan rate of 4.7 percent. But even more telling is the little-known statistic known as the labor force participation rate. Capturing the percentage of adults either working or looking for work, the rate in Detroit stands at just 53.4 percent, far below the national average and the lowest among 40 cities reported by the U.S. Bureau of Labor Statistics.

Economists say a low participation rate in the job market reflects a large population of poor people, elderly residents and young people with low educational attainment. It also tends to correlate with a high unemployment rate, since low labor-force participation occurs when jobs are scarce.

It is particularly worrisome for Detroit because at a time when baby boomer workers are aging out of the workforce, employers need all the new candidates they can find.