Even this is probably not very meaningful. Seasoned and experienced Ada programmers are likely to come from a high-level (software) engineering background in s

Even this is probably not very meaningful. Seasoned and experienced Ada programmers are likely to come from a high-level (software) engineering background in some large company, e.g. in the aviation industry or military. Haskell programmers will more likely work in academia, e.g. a professor of computer science. And the C++ programmers could come from any field or industry. These people will likely shine with certain tasks and be less productive with other tasks, depending on their varying skill sets. So you're probably only measuring the overall level of proficiency of programmers of certain languages in a particular programming domain. For example, I'd bet that the average experienced C++ programmer is slightly less skilled than the average experienced Ada programmer (if both of them are mostly working with their language professionally), simply because C++ is more widespread whereas the few Ada jobs left require a relatively high level of expertise. On the other hand, if you're writing programs in Ada for Airbus, you're probably accustomed to a slower development pace than if you write C++ code for a small gaming company, so the "productivity" will appear to be fairly low in comparison. Then there are measures like LOC that are fairly meaningless across languages and perhaps even in general. Finally, languages are usually chosen for their tool and library support and on the basis of available developers anyway.