Natural Growth Rate

In demography and population geography, the natural growth rate (NGR) is the difference between birth rates (BR) and death rates (DR), that is, NGR = BR–DR. Along with net migration, natural growth rates are one of the two fundamental components of demographic change. For the world as a whole, natural growth rates are the only measure of population change, although for any unit less than that both natural growth and net migration must be taken into account.

Historically, natural growth rates have been very low, often zero, and at times, when mortality exceeded fertility (such as during famines or plagues), even negative. Only with the Industrial Revolution and the concomitant reductions in death rates (not a rise in birth rates) did natural growth rates rise, leading to an exponential increase in the world's population level (Figure 1). Thus, rapidly growing societies are essentially a product of modernity. Thomas Malthus, the founder of the notion of overpopulation, observed the rise in natural growth in late-18th-century England to sound the alarm that such increases would offset any economic gains, although his conclusions were rendered incorrect by the exponential increases in productivity that industrialization generated.

Natural growth rates vary widely around the world (Figure 2) and reflect the multitude of social, economic, and political factors that shape the geography of birth and death rates, particularly wealth and poverty. Because mortality rates have been to a considerable extent equalized worldwide, the major variations in natural growth rates are mostly attributable to differences in birth rates. Such patterns are largely explainable by appeal to the demographic transition. Generally, the poorest countries have the highest birth rates, and thus the highest natural growth rates, as in parts of Africa and the Arab world. Frequently, rising incomes lead to lower birth rates and smaller families, as in Europe, North America, Japan, Australia, and New Zealand. In many economically developed countries, where death rates exceed birth rates, natural growth may be essentially stagnant (i.e., zero population growth) or even negative, as in much of Eastern Europe and the Soviet Union as well as parts of Southern Africa afflicted by the AIDS crisis, indicating that whatever population increase occurs is due entirely to immigration.

Overall, as global fertility rates have de clined, so too has the average worldwide natural growth rate, which is widely expected to continue dropping [Page 1982][Page 1983]in the foreseeable future (Figure 3). Thus, whereas the world's natural growth peaked in the mid 1960s (around 2.3% annually) and dropped to 1.3% in 2007, it is projected to fall as low as 0.5% by the year 2050.

Figure 1 World population level, 7000 BC to AD 2000. The dramatic explosion in the world's population since the Industrial Revolution reflects the decline in mortality rates that it fostered.

Source: Author.

Figure 2 Natural growth rates, 2007. Variations in natural growth around the world primarily reflect differences in mortality rates; some countries experience negative natural growth.

Source: Author.

Figure 3 World natural growth rates since 1950 and projected to 2050. Gradual declines in fertility worldwide have led, and are expected to continue to lead, to declines in the world's population increases.

source: Author.

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