First, my only guess is that everyone's guesses are going to be wildly wrong. People who work in such spaces will greatly overestimate. People who don't will greatly underestimate. (This is mostly due to how many comments I've read on HN that implicitly assume that most people's problems and perspectives are the same as the commenter's.)
Second, linked lists are useful in a lot more places than that. Probably a better proxy would be low-level coders. You almost always want a linked list somewhere when you're dealing with memory addresses and pointers. Maybe not for the primary collections, but there are always secondary ones that need to maintain a collection with a different membership or ordering, and vectors of pointers don't have many clear advantages over intrusive linked lists for those secondary collections.
Yeah intrusive collections in C is the biggest use I’ve seen. I played with a physics engine a few years ago (chipmunk2d) which made heavy use of intrusive linked lists to store all the objects in the world model. I suspect there’s some clever data structures out there that might have better performance, but the intrusive linked list approach was simple and fast!
More like 0.01% -- if we consider enterprise programmers, web programmers, and application/game programmers which I'd expect to be the largest groups...
Yep. There aren't many software developers I know who have ever touched {Linux, macOS, FreeBSD, Windows} kernel code except for embedded devs, driver devs, security researchers, hobbyists, and SREs/PEs.
The % who have touched kernel bits, wrote a triangle engine scene renderer, wrote a compiler, touched server metal in production, have worked on ASICs, and can put together ML/AI building blocks shrinks way, way down to a handful of living humans.
This not about blue collar vs white colar. After all corporate programmers and web programmers can both be blue colar, and systems programmers can be white colar (if we're using "blue colar" to mean smaller salaries and fewer percs - otherwise programming is a white colar job anyway).
This is about how many work in kernels/embedded systems/etc vs more common programming gigs. And that's less about how many are trained to do so, but rather how many are needed.
Second, linked lists are useful in a lot more places than that. Probably a better proxy would be low-level coders. You almost always want a linked list somewhere when you're dealing with memory addresses and pointers. Maybe not for the primary collections, but there are always secondary ones that need to maintain a collection with a different membership or ordering, and vectors of pointers don't have many clear advantages over intrusive linked lists for those secondary collections.