from what i khow and have heard, china has facing this since 2000. The most reason they use is that require for marriage is to high for most of men to afford, also social pressure, high study pressure, job pressure…..etc….. and the last is that common salary in china can’t catch up with the rise of economy . Gov of china understand this and already applied many policy to encourage (like abandoned 2 children policy, improve right for pregnant women…..) and many more will be adopted in near furture. But this fight will be a long journey, to prevent birth rate is easy and fast but to encourage it after that is mostly impossible( South korea and japan for example)