A number of countries and communities do not have large enough a population to survive. In some cases this is due to birthrates being below 2.1 children per woman of childbearing age, the acceptable figure for sustained reproduction of a population. In other cases, a net out migration has caused the underpopulation.
In Russia in the 1990's, the birth rate declined to 1.3 births per woman while the life expectancy of men fell to 57 years, which last has been blamed partly on rising alcoholism.
Deaths per year in the early 1990's exceeded births by 800,000, so the population has fallen in absence of war, famine or epidemic disease.
Despite rapid population growth, Africa remains under-populated: its population density of 249 per 1,000 hectares is low compared to the world average of 442 or the 1,130 found in Asia (WRI, UNEP, UNDP and WB 1998).
Fertility in modern Western democracies has fallen below the replacement level. Unless there is a sharp increase in the size of its families, the West will lose out to other regions of the world, notably to the Third World.
A cause of population decline in the absence of national disaster is social malaise. Governments do not concern themselves closely enough with public health, so environmental pollution, drug and alcohol addiction, and underequipped health services cost many lives. People choose not to take on the task of bringing up children because their own daily survival is too precarious or difficult, which also increases the tendency to suicide.
In Russia, the number of infant deaths due to congenital abnormalities rose consistently from 1990 to 1993, when it reached 436 per 10,000 children, a rate 4 times that of the USA. Congenital deformities are increasing faster than any other health problem in Russia. They are thought to be due to irresponsible chemical and radioactive environmental contamination.
In Russia the number of deaths directly caused by alcohol rose from 9.3 per 100,000 in 1986 to 37.8 per 100,000 in 1994.