Both the intrinsic rate of increase (r) and the finite rate of increase (X) are used commonly to track population growth and to compare growth rates among populations of the same species found in different environments, as well as among different species. Consequently it is important to understand the relationship between X and r. As defined in Equation 1.5, X is the growth rate per time period (usually per year) and is based on the ratio Nt+l/Nt. If the population lacks an age distribution or has a stable age distribution (SAD), the finite rate of increase, X, is a constant. The population as a whole and each age class will grow

Table 1.5 Human demographic trends in Asia since 1981. Data from the Population Reference Bureau (Anonymous 1981-2004).

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