Underpopulation is usually defined as when a country's population has declined too much to support its current economic system. A simple example would be if all the retired people were supported through a sort of social security system, and then a generation only had an average of 2 children, compared with the last generations average of 3 children. In this case, the younger generation may not be able to support the older generation, and problems could erupt.

The essence of underpopulation is that it is defined and a result of the system in place in the country. It does not have to do with the population numerically, but only relatively, and is not usually opposed to overpopulation, which deals with the total possible amount of population desired.

It is widely believed that there will be an underpopulation crisis in Japan by 2014, which is unsolvable except by massive immigration. It is also believed that there could be the same crisis in Western Europe, however immigration there may help to offset the crisis. Problems could arise in Eastern Europe and Russia too, where the natality fell abruptly after the end of Communism. Underpopulation is also believed to be the root cause of the possible future failure of the United States Social Security system, but, until now, the constant flow of immigrants delayed the problem.

According to more recent reports by the United Nations Population Division (World Population Prospects - The 2002 Revision) and the US Census Bureau (Global Population Profile: 2002), underpopulation is becoming an imminent danger. In the former report, below-replacement fertility is expected in 75 per cent of developing countries by year 2050. In the latter report, the Census Bureau noted that the 74 million people added to the world's population in 2002 were significantly fewer than the high of 87 million people added in 1989-1990. The growth rate was a meager 1.2 percent, down from the high of 2.2 percent in 1963-64.

"Census Bureau projections show this slow-down in population growth continuing into the foreseeable future," stated the Bureau's brief on the findings. "Census Bureau projections suggest that the level of fertility for the world as a whole will drop below replacement level before 2050."

The Bureau attributes the dropping growth rate to two major phenomena – the AIDS epidemic and declining fertility rates, including increased contraceptive use. "In 1990 the world's women, on average, were giving birth to 3.3 children over their lifetimes," said the Census Bureau. "By 2002 the average was 2.6 – less than one-half of a child more than the level needed to assure the replacement of the population."

See also

• Overpopulation
• Sub-replacement fertility

External links

• BBC Report 2004: World population growth 'falling'
• 2002 Revision of the official United Nations population estimates and projections
• BBC Report 2000: Eastern European population to plummet by one third