[acdha]

My interpretation of that is both that we need more research and that this is a very hard problem to study. One of the big challenges is that the things which are easy to study aren't representative of real world conditions: if you have CS undergrads doing new development on toy problems, that isn't representative of what experienced developers at most businesses do. Having people pick less common languages can select for programmers who aren't representative of the general field[1] and are probably going to invest extra time making their favorite language look as good as possible. You can hire people, train them in various languages, and have them implement something generally applicable but that's now a really expensive study.

1. e.g. what percentage of the gains attributed to Lisp were more likely due to the candidate pool in the 90s/2000s skewing heavily towards people who learned it at elite CS programs, especially if you're doing a challenge competition which benefits from having studied various algorithms?