Programming knowledge by language

There are lots of programming languages. There are many programmers that use these languages. I wonder how many programmers know how many languages and which ones they know. For example, I’d be surprised if there are many Scheme programmers that know only Scheme, but I know there are many Java programmers that have only ever used Java. I’m curious about what distributions there are — how many of the programmers out there know how many languages each. Where are the clusters? “Programmers that like/use language X are likely to hate language Y.” Someone must have done research on this, but I haven’t managed to find any in the ten minutes I’ve been looking for it.