According to publicly available data from the Department of Labor’s Wage and Hour Division, the agency is relying on outdated wage survey data in some jurisdictions. Using data from the 1980s means that wages are lower than what would truly be “prevailing” during today’s economic times.
Former Wage and Hour Division head David Weil said that the Labor Department is in a difficult position given the length and complexity of the surveying process and the limited resources available to execute it.
See here for more information: https://www.bloomberg.com/news/articles/2018-05-25/these-u-s-workers-are-being-paid-like-it-s-the-1980s