The 'relative' graph is rubbish. The 'absolute' graph says something that I think is fairly obvious: If you want a job, you'll have an easier time finding it if you can write Java (or C++, or C#).

I did a bit of clicking around, and most of the Ruby jobs were for Ruby on Rails, which is a little disappointing, but not surprising.

Most of the Python jobs seem to mention python as a secondary skill next to PHP, or are otherwise a massive mash of keywords. Which is even more disappointing; even though I'm more of a Ruby guy, Python is an excellent language for any serious number crunching. I can't think of anything in any other general-purpose language that comes close to SciPy/NumPy.