Natural growth is the difference between fertility and mortality rates, expressed as a rate per 1,000 people per year. Thus, in addition to net migration, the natural growth rate is one of the two major means by which populations change in size and composition. For most societies, natural growth greatly exceeds migration in importance.

The natural growth rate is a reflection of the complex forces that underlie the social and spatial dynamics of both fertility and mortality. Some of
these are biological in nature, including genetics, which shapes birth and death rates and life expectancy. Most, however, are socially constructed and include, among other factors, relative access to food and healthcare, the quality of drinking water, the structure of employment, the costs and benefits of having children, state policies, and cultural preferences for large or small families.

Natural growth rates vary widely over time and space, reflecting the particular social, political, cultural, and economic relations of individual societies. In general, in impoverished preindustrial societies prior to the modern introduction of antibiotics, where both fertility and mortality rates are high, natural growth the difference between births and deaths tends to be low. Indeed, for most of human prehistory, and world history until the Industrial Revolution, natural growth hovered around zero.

Only with industrialization and, in particular, the development of an adequate and reliable supply of food, as well as improved drinking water and public health measures, did mortality rates begin to decline. Thus, natural growth rates are intimately associated with the demographic transition. In societies where fertility rates remain high but mortality rates have dropped, natural growth rates tend to rise markedly. Throughout the world today, where mortality rates vary much less than do fertility rates, natural growth is highest in economically developing countries. Thus, in much of Africa, Asia, and Latin America, natural growth rates often exceed 2.5% annually; in some countries, they exceed 4.2%. However, as fertility rates have declined worldwide over the past five decades, so too have natural growth rates. World average natural growth dropped from 2.6% annually during the 1950s to roughly 1.4% today. In the economically developed world, where birth rates often have dropped below death rates, natural growth rates often approach zero population growth or, as in the cases of Japan and most of Europe, are negative, leading to demographic decline. In such countries, net immigration becomes an important source of population growth and supply of labor.


Ozenk Articles - Pertumbuhan alami