NCWIT Scorecard has great statistics and references. While the report’s title is “Why is gender diversity important in computing?” much of the supporting research references different kinds of diversity. Here’s a high level snapshot:

Diversity

• Expands the Qualified Employee Pool
  We’re not taking advantage of our diverse population. The industry is failing to attract
  this talent. Indeed, those women already employed in the technology industry are
  leaving at staggering rates, so we’re not retaining either.
• Improves the Bottom Line
  Technology companies with the highest representation of
  women in their senior management teams showed a higher return on equity than did
  those with fewer or no women in senior management.
• Enhances Innovation
  A large study spanning 21 different companies showed
  that teams with 50:50 gender membership were more experimental and more efficient.
  Extensive research has found that groups with greater diversity solve complex problems
  better and faster than do homogenous groups. Culturally diverse teams have been shown
  to generate a wider variety of possible strategies when setting a course of action.
• Promotes Equality
  With technology playing an increasingly crucial role in all of our
  lives, having more people from different backgrounds participate in its creation can help
  break down gender and racial economic inequalities.
• Reflects the Customers
  Most companies serve a variety of people, so it makes sense then to have a variety of intelligent, skilled people working on services and products.

Read the full report