1. The population explosion seen from human history

Several decades have passed since warning phrases such as "the population explosion," "population bomb," and "Spaceship Earth" provoked grave concerns among experts all over the world. Concerns over limits of the food supply to support human survival and the deterioration of the environment were widely shared. However, people have little interest in demographic changes that constitute the fundamental elements for such concerns. What is the reason for this?

It is said that human beings originated 2 million to 3 million years ago. The process of population increase in this long history is extremely complicated. The trends of vital statistics of fertility and mortality that determine population increase rates have been indefinite. Of particular significance are the impacts of epidemics and famine on the reduction of population. At times, epidemics and famine were so serious that the populations of the affected areas could hardly increase for years.

The process of increase in the world population since the Neolithic Age, about 10,000 years ago, to today is shown in figures 1 and 2. Surprisingly, an agricultural revolution occurred as early as about 8000 B.C. As a food production system, it helped stabilize the survival of human beings. The world population at that time is said to have been between 5 million and 10 million, and increase rates were nominal.

As seen from the figure, it was in the 18th century that the near-zero increase rates had reached the 0.4% level, after which the rates gradually increased to reach 0.8% in 1950. The rates further increased to 2% or more when the too-high population increase was given the label of "population explosion." The second starting point of the world population explosion might be found in the industrial revolution and modernization that brought economic development and advancements in medical technologies and public health services, through introducing stable population increase rate due to higher fertility and lower mortality.

2. The end of population explosion and population stabilization

It should be understood that the phenomenon of population explosion is not a transitory demographic change but a fundamental problem relating to the very survival of human beings on the earth. This has actually resulted in the problem of under-replacement fertility and population aging, which are considered as demographic consequences of the population explosion. The storm of the population explosion is beginning to settle with the advance notice of declining increase rates at the global level. Furthermore, people's perception has increased as to the limit of capacity of the earth to support humans. The world population projections made by the United Nations and other institutions offer grounds to seek a new order in world population.

3. Stability of the world population order and imbalance in distribution

The threat of explosive increase may be eased by considering the relationship between the total world population and resources provided by the earth. However, a notable change in geographic distribution caused by changes in age structure and differences in vital statistics may greatly affect the economic, social, and power structure systems of the world. It cannot be denied that the political order developed in the past centuries might be destroyed from the ground up.

Figure 1 and 2: Increase of World Population