Comment by cnorgate

For what it's worth, I believe they took a sample of close to 600 people - 237 from Harvard, and another 332 who were less 'advantaged'

http://en.wikipedia.org/wiki/Grant_Study

Yes, they were all white males. Not a great study if they were trying to definitively answer the question for everyone in America. But to suggest the findings have no broader applicability would also be short sighted.