A Fascinating Puzzle!

A colleague alerted me to this fascinating puzzle that is doing rounds on the internet. I spent an hour trying to figure it out. It sounds pretty innocuous (but like all great puzzles, it is very nuanced):

In a country in which people only want boys every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country?

The "official" answer is 50-50, although you may be inclined to think that such a country would overproduce girls.

Spoiler: Here's a link to a great answer and discussion. Try not to peek at it before you give it a shot.