The U.S. economy made big strides in October.

And one of the brightest spots was that a lot of America's part-time workers have been able to find full-time work.

The number of part-time workers who would rather have full-time jobs has fallen by more than 1 million to 5.7 million in the past 12 months. It's the lowest number since 2008.

"It's a real sign that the labor market is healing," says Douglas Holtz-Eakin, president of the think tank American Action Forum.

The rise in part-time workers has been one of the most unsettling trends of the Great Recession and the years since. Most of these workers are doing it not out of choice but because they haven't been able to find full-time work.

There's a lot to worry about. Part-time workers -- defined as people working under-35 hours a week -- are five times more likely to live in poverty than full-time workers, according to a report by Rebecca Glauber, a professor at the University of New Hampshire.

The majority of these workers are also in low-wage industries like retail and restaurants.

They are far less likely to have health and other benefits. Part-time workers often get fewer and smaller wage hikes than full-time workers who have the same responsibilities, says Chris Tilly, a professor at UCLA.

Related: Part-time jobs put millions in poverty or close to it

One reason that part-time workers have been stuck with fewer hours is because employers have been afraid about higher costs associated with full-time workers, particularly healthcare costs. The Affordable Care Act mandates that companies provide healthcare to their full-time employees.

Many large companies, including Home Depot (HD)and Walmart (WMT), have cut workers' hours or healthcare benefits, citing the Affordable Care Act. The high healthcare costs remain a concern, Holtz-Eakin says.

Still, this decline in part-time workers is a broad sign that the American job market is stronger. As more people find jobs and there's a smaller supply of available workers, employers must upgrade workers from part time to full time -- or risk losing them to competitors.

And when more people get full-time work, wages go up. That's exactly what happened Friday -- wages for everyone grew 2.5% in October -- the best one-month gain in years.

It also reflects optimism on the part of business owners.

"When people are able to work full time instead of part time, that tells me that businesses are more confident," Tom Perez, U.S. Secretary of Labor, told CNNMoney Friday.