Competition
Simply put, the more developers, the higher the job competition. Languages with a wider following are also going to have more people vying for available jobs.
low / Competition / 3 total
C
Used for hardware systems programming drivers
low barrier to entry
low demand
high pay
medium to find help
Elixir
Used for websites hardware multimedia processing realtime communication
medium barrier to entry
medium demand
high pay
hard to find help
Rust
Used for websites video games desktop apps hardware embedded software
medium barrier to entry
medium demand
high pay
hard to find help