The Washington Post reports that most diversity training efforts at American companies are ineffective and even counterproductive in increasing the number of women and minorities in managerial positions.

A comprehensive review of 31 years of data from 830 mid-size to large U.S. workplaces by the University of Arizona found that the kind of diversity training exercises offered at most firms were followed by a 7.5 percent drop in the number of women in management. The number of black, female managers fell by 10 percent, and the number of black men in top positions fell by 12 percent. Similar effects were seen for Latinos and Asians.

So what’s the problem?  It seems that it’s the mandatory programs, often undertaken mainly with an eye to avoiding liability in discrimination lawsuits. When diversity training is voluntary and undertaken to advance a company's business goals, it was associated with increased diversity in management. The research found is that programs work best when they focus on specific organizational skills, such as establishing mentoring relationships and giving women and minorities a chance to prove their worth in high-profile roles.

Frank Dobbin, co-author of the study, also made the interesting point that women and minorities often fail to get ahead because people tend to form social groups with others who are like themselves, and many managers are simply unaware of the talent in their own organizations. Policies that require or explicitly encourage managers to meet with subordinates in different departments can alert managers to talented employees with different social and ethnic backgrounds and help younger employees figure out what they need to do to get ahead.

The impact of this research has yet to be seen, but at least it’s opening up people’s eyes to the fact that some corporate ceilings are still pretty unbreakable.