Manufacturing jobs - in particular, auto manufacturing jobs - used to pay better than other types of jobs.
After 2007, that was no longer the case, according to a new analysis by the National Employment Law Project.
The trend continues to worsen.
The report finds that manufacturers earned 7.7% less than the median wage for all occupations in 2013.
More than 600,000 manufacturing workers make just $9.60 an hour, or less.
Real wages for auto parts workers have declined even faster than for manufacturing as a whole. Auto manufacturing real wages fell by nearly 14% from 2003 to 2013.
"There's no question that manufacturing jobs are going to join the ranks of fast food and other low paying service jobs," if nothing is done, says study author Catherine Ruckelshaus of NELP.
Ruckelshaus says about three-quarters of auto workers are now employed in parts plants, not auto assembly plants. Wages in auto parts plants are lower, and many of the facilities are non-unionized.
In addition, many manufacturing a facilities are employing large numbers of temporary and contract employees - and those workers' wages are lower still.
However, since the federal government no longer tracks those wages, Ruckelshaus was unable to include the data in the report.
Ruckelshaus questions why states and cities woo manufacturing concerns with big tax breaks and grants, since the jobs often are not good jobs with good benefits.