US State Salary History Bans — Removing Past Pay from Hiring Negotiations (Massachusetts 2016, California 2018)

Salary history bans (SHBs) prohibit employers from asking job applicants about, or relying on, their previous pay. Massachusetts enacted the first statewide ban in 2016 and California followed in 2018; roughly a dozen states had adopted bans by the time of the studies cited here. The rationale is that anchoring offers on past pay carries earlier pay inequities into each new job.
Evidence: Hansen & McNichols (NBER Working Paper 27054, 2020), using difference-in-differences and synthetic-control designs, found the gender earnings ratio rose by about 1% in states with bans, driven mainly by workers who had recently switched jobs. A later study in the Journal of Economic Inequality (Bessen, Meng & Denk) found that after bans employers posted wages more often and raised pay for job changers, by 6.2% for women and 5.8% for non-white workers, with no evidence of adverse employer reactions in the short run.
A field experiment by Barach & Horton (Journal of Labor Economics, 2021) in which employers could not see compensation history found they evaluated about 7% more applicants and hired workers with 13% lower past wages, who then bargained better wages, showing the mechanism works.
Limits: gains are concentrated among job switchers and are small relative to the overall gap; applicants can still volunteer their history, and research reports that men disclose more often than women, which can erode the effect. The ban is a low-cost, legislative measure with no direct public spending, but it addresses only one channel of the pay gap and is best combined with pay-range posting and pay reporting.

Read the full analysis: https://www.nber.org/papers/w27054