Research conducted by Stanford Graduate School of Business shows that several variables statistically have very different impacts on the funding success of loans. E.g. a group leader endorsement is twice as effective as improving one credit grade.
This study is a must read for group leaders and is very interesting for lenders too.
Source: https://www.prosper.com/prm/3rdParty/Prosper_Regression_Project_-_Fundability_Study.pdf