Taking census of physics

• https://www.nature.com/articles/s42254-018-0005-3

A study of Physics papers and Physicists.

identify the subfields of 135,877 physicists and quantify their heterogeneous birth, growth, and migration patterns among research areas.

The paper used PACS code to define major areas.

Using statistical tests to define physics papers, assign field labels to all papers, and then assign field labels to physicists.