I've heard people say (although I can't recall who in particular) that the number of bugs per line of code is roughly constant regardless of what language is used. What is the research that backs this up?
Edited to add: I don't have access to it, but apparently the authors of this paper "asked the question whether the number of bugs per lines of code (LOC) is the same for programs written in different programming languages or not."
One possible source would be Les Hatton's 1995 paper "Computer programming languages and safety-related systems", in which he concludes that language choice is at least close to irrelevant and other factors (chiefly fluency in the chosen language) are the controlling factors. Unfortunately, I don't know of an electronic copy available online -- the link is only to his synopsis (though it does include an email address to contact the author).
About all I could add to that would be to summarize various other papers, in which defect rates for individual projects (and such) are given. I've done a bit of looking, and never found a correlation between language and defect rate, but that's not really the same as saying the defect rate is constant across languages (i.e., they may be different, but they vary so widely within each language that I've never been able to prove a difference).