It's not like they have a choice man. A part of it is due to culture and norms associated with it. About that 1 child per 1 family policy - gotta do what you gotta do if it may seem crude, when the country's overpopulated.
Population of China:
1,330,044,544 (JUL, 2008) EST.
Population of USA:
303,824,640 (JUL, 2008) EST.
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Difference: 1,026,219,904 people. that's for every one person we have here, they have four.
Size of China ~ 3,696,100 sq mi
Size of USA ~ 3,676,487 sq mi
It's almost 1:1. You see how cramped that is? Get an idea.. same size as the US, but four times the people.
Think of Berkeley with 4 times the hobos out on the street, 4 times the crazy people wandering around College Avenue, 4 times the students on campus, 4 times the people ordering pizza in that one family pizza shop down campus, 4 times the dudes checking out that CHOC store.. I'm sure you're getting my point. It's pretty damn congested already in Berkeley, I can't imagine it getting worse.
Now I understand that sterilization is NOT the human way to resolve this. But think of it, how would you solve this when theoretically each baby born means more burden to the country?