[terranstyler]

If you want to learn the language for the pleasure of speaking it, you may find it easier to find Spanish speaking people, especially in the Americas.

If on the other hand you want to increase your market value, going the extra mile might pay off since the supply of German and Japanese speakers is probably smaller by an order of magnitude while the GDP (as a proxy for the economic value of the language) is comparable and much denser.

For English speakers German should also be much simpler than Japanese.

http://www.economist.com/blogs/prospero/2014/03/language-stu...

[BuckRogers]

I think there are other factors more important than economic. That is probably one of the worst metrics to base any decision on. If the goal is money, there are many ways to get it without learning a language. Seems like an odd primary concern for language learning. That said, keep in mind that Germans and Japanese people have a much easier time learning English due to it's ubiquity than the OP would theirs, making his employment less attractive to just hiring a local who knows English. Also, going forward, there's a much better chance the spread-out Spanish 'world GDP' will increase somewhere by a large amount. The German and Japanese speaking world are maxed out on GDP potential today. Likelihood of expansion of either died with WW2.

Spanish is an unstoppable train like English has been. It's the safe bet on all fronts, and exporting its culture unlike the insular Chinese languages have remained. An American is lucky to have that be a de facto 2nd language to learn. Much of the world is stuck with something far less relevant going forward (other than English). Even French in Canada, hard to choose Spanish over French if Canada.. yet Spanish is by most metrics the better choice. That with French being one of the better choices, most nations neighbor's have even less relevant languages as an obvious 2nd language choice.

That said, the easy answer is to learn what you have an interest in. Let the money follow that.