The article that included the graph below surprised me:
The gist of the article is to note that in 2012 (the year graphed above), markedly fewer programmers are working in a single programming language. The article has the same data for 2010, and indeed there are many more programmers working in a single language just two years earlier.
The surprise for me isn't that we have more multiple-language programmers – it's that we have so many single language programmers, even today!
Certain kinds of programming, much less common these days, perhaps can be done with a single language – things like embedded systems, low-level systems programming, etc. But surely it isn't true that close to 20% of all programmers fall into these categories? I'll speculate that on some larger teams, it's possible to write for years in a single language because you're slotted into some narrow area of work. I still have trouble imagining 20% of all programmers fitting into that category.
So I'm surprised!