in china one family has only one child recently.how do you y

不知道你要的难度,权且按照学术论文的标准帮你找了几篇.
Smaller,Happier,Harmonious Families:China’s One Child Policy
Can China Afford to Continue Its One-Child Policy?
The Effect of the One-Child Policy on Fertility in China:Identification Based on the Differences-in-Differences
How Effective is the One-Child Policy in China?
Effects of the One-Child policy on the Number and Sex Composition of Children in China
如果你开不了国外网页可以告诉我你的邮箱,我把文章发给你也成.

Google 一下，"one-child policy in China", or "China's one-child policy". Good luck.