WASHINGTON (AP) — While the U.S. economy has improved since the Great Recession ended five years ago, part-time and so-called contract workers are filling many of the new jobs.

They are a diverse army of laborers that include janitors, security officers, home-care and food service-workers and computer programmers. Many are involved in manufacturing. Others are self-employed, under contract for certain responsibilities fulfilled by specific deadlines.

Contract workers made up less than half of 1 percent of all employment in the 1980s but now account for 2.3 percent. Economists predict contract workers will play a larger role in the years ahead.

Labor leaders and many economists worry.

Contract workers have less job security and don't spend as much as permanent, full-time workers. Nor do they have the same job protections. Few are union members.