I'm not sure how you quantify "very small" here? I'm running low-level conferences [0] and they're big enough for me to be a full-time organizer for them: with a job fair that's included Mozilla, real estate, nuclear defense and various game studios.
We could check popular job boards (or HN's Who's Hiring threads) and see how many postings mention compilers, kernels, assembly, GPU, etc. Then compare that number to the total.
[0] https://handmadecities.com