http://www.amazon.com/Affirmative-Action-Around-World-Empiri...
The Russians came up with an unusually crass method for this, but guess what? Jews and other whites and East Asians all are, to some degree, kept from elite institutions today because of our more subtle system.
How do we improve natural diversity? Through persuasion, not coercion. That means, first and foremost, improving education for people and instilling the right cultural values so that they have the right skills and qualifications. When we have diverse people with the right skills, diverse workforces occur naturally in a free market system.
Finally, people who think America has a huge racism problem should travel across the world now and also read history better. America is one of the least racist places overall in recorded history. It's something we can always improve on, bu, at this point it's just another problem among many, and our overemphasis on it is also causing far more problems than helping people.