Introduction Only 40 years ago, population experts were still worried about a population explosion that would threaten the future of humanity. Fortunately, while population growth is currently largely under control, sub-Saharan Africa and parts of South Asia still face massive increases with very serious potential consequences.1 Paradoxically, however, a new problem is emerging, with its key locus in Pacific Asia (the term used in this book to refer to Asian countries with a Pacific littoral). This problem is ultra-low fertility. Japan, Singapore, Taiwan, South Korea, and Hong Kong SAR are among the very lowest-fertility countries in the whole world, and even China has reached fertility levels lower than those in many European countries. Fertility has sunk so low in many East Asian countries that if these levels continue over long periods, populations will face accelerating population decline not very far into the future. Not only this, but changes in age distributions in such populations raise major new questions for planning of economic and social welfare. The best-recognized prospect raised by ultra-low fertility is population aging, which brings with it an entirely new set of issues, for example, increasing old-age dependency ratios, financing old age and old age health care, continuing familial support of the elderly and elderly political participation. But there are many others, for example, the decline in size and changing age structure of the workforce, and the declining visibility of and perhaps attention paid to the needs and interests of children and young people.