Looks like as far back as 2014 research has pointed to some big gains using HTTP/2 push: https://dl.acm.org/citation.cfm?id=2578277 https://dl.acm.org/citation.

Looks like as far back as 2014 research has pointed to some big gains using HTTP/2 push: https://dl.acm.org/citation.cfm?id=2578277 https://dl.acm.org/citation.cfm?id=2578277