Research by Casey suggests that , over all subjects , PhDs provide an earnings premium of 26 % over non-accredited graduates .
Research by Casey notes that master 's degrees provide a premium of 23 % and a bachelor 's 14 % .
Research by Casey suggests that , over all subjects , PhDs provide an earnings premium of 26 % over non-accredited graduates , but notes that master 's degrees provide a premium of 23 % and a bachelor 's 14 % .