Probably Java (or other JVM lang) running something like Disruptor for high performance, or actor based libraries like Akka for general use case. No numbers, but considering how it's used in nearly all the bigger tech and finance companies, I'm guessing it probably has more use as a highly concurrent platform than anything else discussed here.
Another reason for their usage of the JVM could be because a lot of these languages specifically designed for concurrent programming either didn't exist or were in their infancy of real-world usage. Erlang was proprietary until 1998, and Haskell was not created by a large company. In the meantime, Sun was pushing Java everywhere they possibly could. So it makes sense that larger tech and financial firms, especially those who established themselves in the late 1990s (or descendants of such companies), would use the Java platform. There were also a lot more Java developers than Haskell developers, and there still are, and that's a big part of the decision-making process when choosing a platform.
Forget familiarity, hot code loading, and the huge library ecosystem (the largest in computing history) compared to one of the tiniest, but Java's runtime monitoring is far, far ahead of anything Haskell (or any other language or platform) can provide, and while Erlang's is pretty impressive (a close second), it is still not on the same level as Java's.
The standard JVM's don't support lightweight threading (like Go's Goroutines)...so yeah while you can do concurrency with callbacks, or "actors" (callbacks with lipstick on), it's not quite the same thing.
