Some Asian countries, including India and China, have (RNI) geodemographers subtract the death rate from the birth high sex ratios. India’s sex ratio is 113 but rises to 123 in rate and convert that ﬁgure to a percentage. For example, in some northwestern states. In 2005, China’s sex ratio was 2009 the birth rate for the world was 20 per 1,000 and the 120, and there were 32 million more men than women under death rate was 8 per 1,000. The difference is 12 per 1,000, the age of 20. In China’s rural provinces, where couples are which, when converted to a percentage, yields a rate of natupermitted a second child if their ﬁrst is a girl, the sex ratio ral increase of 1.2%. This ﬁgure may seem low, but we should for second births exceeded 160. In both countries, a strong keep in mind that even a small percentage increase translates cultural preference for boys is partly responsible for these into a large number of persons. In 2009, the world population disproportions, but in China the one-child policy also likely grew through the addition of about 80 million people. plays a role. The extremely imbalanced sex ratio for second The rate of natural increase can be zero, as in Ausbirths points to the practice of sex selective abortions to entria, where both the birth rate and the death rate are 9 per sure at least one boy. What are some possible long-term ef1,000. A negative rate of natural increase indicates that fects of such uneven sex ratios? the death rate is higher than the birth rate and there is Geodemographers track the spatial variations that rea natural decrease in the population. With a birth rate of sult from population growth or decline. To do this, they 12 and a death rate of 15, Russia presently has a negative need to know about changes over a given time within a rate of natural increase. Figure 3.8 shows how the rate of natural increase varies around the world. population. In the next section, we will concentrate on the changes to the population through births and deaths. Geodemographers use the rate of natural increase to determine the number of years it takes a population to Later in the chapter, we will look at changes to the popudouble. The population doubling time helps lation through immigration (in-migration) and rate of natural relate current population trends to future popuemigration (out-migration). increase (RNI) lation size. To calculate the population doubling The percentage of Rate of Natural Increase time, you divide the number 72 by the rate of annual growth in a natural increase. This calculation gives a popuA population experiences natural increase when population excluding lation doubling time for the world of 60 years (72 the number of births exceeds the number of migration. ÷ 1.2). If the rate of natural increase remains deaths. To calculate the rate of natural increase

,>ÌiÃÊvÊ>ÌÕÀ>ÊVÀi>ÃiÊ>ÀÕ`ÊÌiÊÜÀ`Ê ÊUÊ }ÕÀiÊÎ°n Where is the population growing rapidly? Where is it stable or declining? Given these trends, what regions are likely to fuel the world’s future population growth? (Source: Population Reference Bureau, 2009.)

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Rate of Natural Increase Over 2.4% 2.0–2.4% 1.5–1.9% 1.0–1.4% 0.1–0.9% -0.5–0.0% No data

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Greiner visualizing human geography chapters 2-5

Chapters for Manual High School