Oh, thank god, finally we get a number. It turns out that I was completely wrong, and that in its 20 years of hyped existence, someone has built something big with Haskell once. You may think I'm sneering, but only a little bit, because while one is almost nothing, it is much better than actually nothing because at least it is a first anecdote. Now, who do I have pester to get some more metrics?
> More details here:
Sadly, there are no more relevant details in that talk.
I am, however, very skeptical of the interpretation some people, especially in typed FP, give to types and the reasons they believe types provide a benefit. For example, the relationship between useful type systems and software correctness is not direct. I am currently using a formal verification tool that is completely logic based (and it has an interactive theorem prover, a model checker, and is backed by decades of careful mathematical analysis of its soundness) which is completely untyped, and yet it is as powerful as Coq for proving correctness of algorithms. If direct, formal, proofs of correctness is what you're after, types might not be the best solution. Types, however, have other clear benefits that are not related to formal correctness, or, at least, not correctness of global program properties.
Low cost of adoption + clear minor tooling benefits is usually enough evidence to adopt Java/C# style static types.
Haskell style static typing has a very high cost of adoption and so must conclusively show a strong benefit in order to be adopted by industry.
At the moment I feel Haskell companies can get away with using Haskell because PL enthusiasts are willing to absorb the training costs.