References on how often finances are cited as a barrier to graduate study

I am looking for some pointers to research that addresses the question:

How frequently do students who have earned undergraduate degrees cite financial barriers as a major reason influencing their decision not to go on graduate study?

Anecdotally, I am personally aware of students who feel that financial considerations prevent them from pursuing graduate study (e.g., they have a family to support and they can't afford to live on a graduate student salary for so many years). I am interested in research¹ that examines the prevalence of this kind of thing (subject to the usual limitations of this kind of survey research, of course).

I have come across studies on how often finances are cited as barriers facing would-be undergraduate students, but I have not seen any equivalent research about graduate study.

---

¹ I am not looking for answers from anecdotal evidence not supported by a study or citation. I am also not looking for answers explaining why such a study is unlikely to exist, or why it should not be trusted if it did