Nature has a lovely, open-source annual graduate survey:

Springer Nature conducted a global survey of PhD candidates in science in 2025, in partnership with Thinks Insights & Strategy, a research consultancy based in London. The survey ran in June and July 2025 and received 3,785 self-selecting respondents from 107 countries. The findings about PhD graduate student experiences are covered in an article series from Nature’s Careers team.

Link to the survey data: https://figshare.com/articles/dataset/Nature_s_Graduate_Survey_2025/30084739/1 The data is rich, and in my pov, very dense in information. Nature already published several articles about it: