I would like to see these sorts of analyses done over time, although I'm not sure it's possible (in the very least it would require a tremendous amount of work)

I would like to see these sorts of analyses done over time, although I'm not sure it's possible (in the very least it would require a tremendous amount of work). Anecdotally in speaking to people who have been in academic research for awhile, things started changing in the late 90s, plus or minus several years. I've heard a similar story repeatedly and independently about different aspects of the system, but in aggregate there's some sense that there has been change in academic research culture that started around that time. I wonder if the relative quality signal of different types of journals has changed dramatically over time.