From the SSRN abstract (via Workplace Prof) of David Bernstein (GMU, law) and Thomas (Tim) Leonard (Princeton, economics), "Excluding Unfit Workers: Social Control Versus Social Justice in the Age of Economic Reform":

...in the early 20th century American labor reformers promoted an ideology that advocated excluding from the workplace those they regarded undesirable, undeserving, or defective. Once progressive ideology came to dominate government policy during the Great Depression, labor legislation was enacted that intentionally set out to exclude "undesirable" workers from the workplace.