I know that trends, researches, and studies often mean nothing. So there's probably more of the same shown here. Some of the data does makes sense though when used in a calendar setting, when looking back in the past.
These charts were created from data kept on Stack Overflow's BBS by entering tag names.
The tags used above were programming languages that I have run into in the last 20 or so years. Languages like Pearl, I consider to be as dead as COBOL, FORTRAN, and BASIC. Ruby is headed in that direction. Objective-C is obviously on the downward trend because it had been canceled after Swift's introduction. Go is still going along. I forgot to add Rust to the tags, which would be crawling behind Go.
Above, we have GUIs being charted. Technically, they are decorated widgets for our OS's default GUIs. I started with X Windows, and obviously Mac before that. But the NeXTs and SPARCs got me interested in designing by own GUI for Microware's OS-9 Level II, which ran on the TANDY Color Computer 3.
Gtk was an ugly version of that GUI I made when I first saw it in Python's built-in library as tkinter, which is only becoming popular because Python is becoming popular. I've tried wxwidgets, and have made videos about how clunky it is. Kivy looks like a modern/contemporary GUI. What you see used on most hand-helds these days.
Qt (pronounced as either "q t" or "cute" still) had a great start coming out of the gate because of its professional design and clean look. And it has remained the easiest GUI to write programs for.