Kate Rockwood

Christopher Cabrera's awakening happened while he was working at a Silicon Valley startup in the 1990s. He was halfway through hiring an eight-person team when his boss pointed out that all of his hires were white guys in their early 20s. "This isn't a fraternity," his boss said--a phrase that haunted Cabrera more than a decade later when he was launching Xactly, a sales-performance-management-platform company.

So imagine Cabrera's surprise in 2014, when...