So "bug rate" is not a real hard metric anyways. And I only have my experience to go on.
But I will say that bugs in Haskell tend to be easier to diagnose (helpful at 2am) and aren't usually bad (although they can be). I have debugged Other People's Code while on-call in Haskell way easier than any other language.
And finally, the vast majority of bugs can be prevented or curbed by the type system. I find every time a Haskell company runs into a nasty bug or annoying issue, libraries that make use of the type system are made that reduce or remove that class of bug entirely. This sounds like you can do it in every language, but really what can be made a "library" in Haskell dwarfs what you can reasonably library-ify in most other languages.
Now, I can't give quantitative evidence of this because I don't even know how I would begin to measure it. But these qualities are definitely a big reason why I don't even listen to job offers that aren't Haskell anymore (going on 10 years of that soon) and I have and will promptly quit a job if the company moves off Haskell.
But I will say that bugs in Haskell tend to be easier to diagnose (helpful at 2am) and aren't usually bad (although they can be). I have debugged Other People's Code while on-call in Haskell way easier than any other language.
And finally, the vast majority of bugs can be prevented or curbed by the type system. I find every time a Haskell company runs into a nasty bug or annoying issue, libraries that make use of the type system are made that reduce or remove that class of bug entirely. This sounds like you can do it in every language, but really what can be made a "library" in Haskell dwarfs what you can reasonably library-ify in most other languages.
Now, I can't give quantitative evidence of this because I don't even know how I would begin to measure it. But these qualities are definitely a big reason why I don't even listen to job offers that aren't Haskell anymore (going on 10 years of that soon) and I have and will promptly quit a job if the company moves off Haskell.