Caplan - Why you should have more kids: http://www.wsj.com/articles/SB10001424052748704289504575313201221533826

Why you'd want to have just 1: http://ideas.time.com/2013/06/11/the-economic-reason-for-having-just-one-child/

Get paid to have babies: http://www.npr.org/sections/money/2011/11/03/141943008/when-governments-pay-people-to-have-babies

Are kids inferior goods? http://freakonomics.com/2011/06/10/the-rich-vs-poor-debate-are-kids-normal-or-inferior-goods/