Global population changes are complex but it can be argued that many countries, but not all, fall into one of two groups, each with very different problems. First, there are the relatively poor, low income, developing countries with high birth rates and rapidly growing populations.Most sub Saharan African countries fall into this group. Second, there are richer, developed, countries with low birth rates and a generally slow growing, static or even falling population. Many European countries fall into this category and they face problems of shrinking labour force, an ageing population and growing welfare bills for pensions and health care. Not surprisingly there is a growing global trend for people to try to migrate from the first group to the second. Countries in the first group include Nigeria, Ethiopia, the Democratic Republic of Congo and many other sub-Saharan countries. In many of the these countries over 50% of the population is aged 18 or under. By contrast, in Japan, the country with the oldest population in the world, some 30% of people are now aged 65 or over and many parts of rural Japan are now shrinking villages of the elderly. The birth rate in Japan is now far below replacement rate (2.1 children per woman) and the countries population is continuing to fall. Many European countries are not too far behind. Italy has 22% of its population over 65 and Finland, Greece, Portugal, Germany, Bulgaria, Croatia, France all have over 20%. But one of the least well known but most remarkable countries is China. It currently has a population of 1.3 bn but this has now peaked and is starting to fall. And, as consequence of Mao's one child policy and the subsequent rapid economic growth, very few families have more than one child and China's population is forecast to almost half by the end of the century on current trends. The problem now facing many affluent developed western countries is the falling proportion of economically active people and a growing, ageing, dependant population of retired people. This poses problems both for the cost of care and the supply of care workers and for expenditure on pensions. Not surprisingly, many young people are trying to migrate from the first group of countries to the second, though both Japan and China have relatively little inward migration from overseas.