In the Prosper Forums, Risk_Reward wrote on incomes versus default rates and that post contained some interesting nuggets.
It has been widely known in credit circles that higher income decreases credit risk. One reference: Sexton D. E. (1977).
On the other hand, credit default risk decreases when the income
and age increase.
According to Carling K., Jacobson T., and Roszbach K’s study,
probability of credit delinquency increases when the income decreases.
So, we expect to find a negative relationship between income and
clients’ payback performance, assuming there is no inflation.
This is another statistics point backing my observation that increasing incomes decrease Prosper loan default rates.