Officials accuse Bridgeview, Ill.-based Drive Construction of setting up two layers of shell companies and paying workers in cash to avoid traceability.

Arguments about prevailing wages have not changed much since the 1980s, the last time the U.S. government changed methods under the 1931 Davis-Bacon Act to determine a prevailing wage on most construction projects with federal funding.

The state recovered more than $44,000 from Minnesota Controls Solutions, which was cited for underpaying and incorrectly classifying its employees.

Proposed changes would be the first major revisions to the law in about 40 years.

Craft-worker wages fell 8.5%, on average and building costs on 335 schools did not drop, say researchers.