The population of the world is distributed very unevenly over the land mass. Approximately 90% of all people are crowded into no more than 25% of the land surface. Variations in population concentration are due to differences in natural or social conditions. Although the proportion of developed countries experiencing difficulties caused by the spatial distribution of their population is smaller than the proportion of developing countries, these difficulties nevertheless occur quite frequently. The industrial mobility necessary to the functioning of the economic apparatus constantly creates problems of adjustment. Some countries are also starting to show concern at the excessive depopulation of rural areas, which has reached its limit, while others must still cope with relatively large-scale migration from the countryside to the towns. The development of new urban centres and the decline and renovation of older ones also present problems for almost all governments. Lastly, problems of environmental protection add a new dimension to spatial distribution policies.
There are three main areas of population concentration. The most prominent is in Asia, where the most densely populated areas are Japan, South Korea, China, Java, India and Bangladesh. Also heavily settled are the greater part of the European peninsula, the northeastern USA, parts of the Caribbean and coastal South America. Non-Soviet Asia, which constitutes not quite 20% of the land surface of the globe, is occupied by an estimated 60% of the world's population, and this percentage is increasing. By contrast, South America, with 13% of the land surface, presently accounts for only 6% of the world's people. World statistics for 1981 indicate that the average population density per square km was: 33 in the world; 99 in Europe; 95 in Asia, 16 in Africa; 16 in North America; 14 in Latin America; 12 in the USSR (in 1978); and 3 in Oceania.
In 1990, there were 4,149 billion people in the developing regions of the world compared with 1,142 billion in the industrialized regions; 78 percent compared with 22 percent. 1994 population scenarios (IIASA, 1994) predict that by 2030, today's developing countries will represent between 85 and 87 percent of the world population. Africa's share of world population will increase most rapidly.