Thanks to Mike the Mad Biologist’s blog, this article (from January 2017) resurfaced:
The new face of US science : Nature News & Comment
This study looks at census data to determine the demographics of PhD recipients in the biological or medical sciences. The authors characterize a biomedical workforce that is fundamentally different from previous generations. Their infographic contains the main trends:

Heggeness et al, The new face of US science. Nature Comment, 2017