I'm... pretty sure that's not due to porn.
Edit: Let me add on-
The Economist wrote:The chief reason for the dearth of births is the decline of marriage. Fewer people are opting to wed, and those who do are getting married later in life. At least a third of young women aim to become full-time housewives, yet they struggle to find men who can support a traditional family. In better economic times potential suitors had permanent jobs as part of Japan’s “lifetime employment” system. Now many of them have to rely on temporary or part-time work. Other women shun marriage and children because Japan’s old-fashioned corporate culture, together with a dire shortage of child care, forces them to give up their careers if they have children. Finally, young people are bound by strict social codes. Only around 2% of babies are born outside marriage (compared with 30–50% in most of the rich world), which means that as weddings plummet, so do births. And even for those who do start families, the rising cost of child-rearing often imposes a de facto one-child policy.
From: http://www.economist.com/blogs/economis ... xplains-16