Sadly, there's very little research controlling for these factors. http://www.hepg.org/hep/Book/5 http://www.hepg.org/hep/Book/5 has a collection of papers tha

Sadly, there's very little research controlling for these factors. http://www.hepg.org/hep/Book/5 http://www.hepg.org/hep/Book/5 has a collection of papers that addresses some of this on the periphery.