Hmmm, for annual income, doesn't this only include the tax payers? Those earning 900/month are not included, no? Admin?

Apart from what Kevin said, I don't have much to add, I think he explained it well.

Just one thing about 900 being a very common wage: "very common" is very subjective actually.

It depends on who you hang out with, your industry, etc. As I moved up the salary ranges, my notion of what salary is "common" changes as well. I used to think that my Director who earned 10k was paid sky high. But now, not anymore.