WASHINGTON — Only two things differentiated Keri Rodrigues Lorenzo from her male colleagues in radio — a higher voice and lower pay.

The difference — sometimes $20,000 less than her male counterparts — grew larger, she said, as she advanced at broadcast stations in Massachusetts and elsewhere. She blamed herself, worked harder, fought it, accepted the reality, and eventually left the industry she loved.

Massachusetts was the first state to adopt an equal pay law, but as Lorenzo’s experience shows, pay for men and women remains far from equal, nearly 70 years after the law passed. Women in Massachusetts earn more than those in all but two states — Maryland and New Jersey — yet still make far less than men, according to a new report by the Institute for Women’s Policy Research, a Washington think tank.