Some regional pockets develop economically and socially dangerous demographics. Despite the long-term and gradual development of demographics, some regional conditions might create surprising problems. China, for instance, has seen tremendous population growth during past decades, resulting in a population of more than 1.3 billion people today. But economic concerns are currently emerging because of low fertility rates. The United Nations' (New York, New York) Population Division estimates that China's current fertility rate of 1.56 will drop to 1.51 between 2015 and 2020—in developed countries, a fertility rate of 2.1 is usually necessary to sustain population levels. A low fertility rate will drive the aging of Chinese society and proportionally higher health-care and social-security costs for a country that has not had to prepare for such cost developments until recently.

In another country, problematic demographic developments have existed for quite some time. The aging of Japan's society is continuing if not speeding up. A recent survey of 16- to 19-year-olds by the Japan Family Planning Association (Tokyo, Japan) found that 36% of male respondents and 59% of female respondents are not interested in or actually despise sex. The association last conducted this survey in 2008, at which time the percentages of young men and women disinterested in or averse to sex were 19% and 12% lower, respectively. Shifting gender roles and expectations appear to be the cause of these changing attitudes toward sex.

Nigeria, in contrast, is one of the countries facing the daunting challenges of unbridled population growth. At present, the country has a population of slightly more than 170 million people; however, because of its fertility rate of 5.5 (as of 2011), the population could reach 300 million in just 25 years. In general, sub-Saharan Africa is a growth region, and it currently accounts for 12% of the global population. Recent projections suggest that the region will account for more than a third of the world's population by 2100.

Regions with declining fertility rates will have to rely on a dwindling workforce to finance an aging population, whereas regions with climbing fertility rates will have to rely on the current workforce to prepare infrastructures capable of meeting the needs of a substantially larger future population.