American corporations held the first diversity sessions in the late 1960s, instructing leaders who were overwhelmingly white and male on how to manage the workplace after the US made it illegal to discriminate against employees based on sex or race.

“The landmark Civil Rights Act of 1965 spawned an era of training . . . in response to the barrage of discrimination suits,” a 2008 review of the programmes in the Academy of Management Learning and Education said. Most managers were given “a litany of do’s and don’ts and maybe a couple of case studies” during sessions that tended to last roughly four hours, the authors found.