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Multilingual Demographic Dictionary, second unified edition, English volume

Vital index

Multilingual Demographic Dictionary, second unified edition, English vol.
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Vital index  (VITAL index)

The ratio of total growth in a given period to the mean population of that period is called the growth rate 1. Occasionally this rate is computed with the population at the beginning of the period rather than with the mean population as a denominator. When population increase over a period of more than one calendar year is studied, the mean annual rate of growth 2 may be computed. In computing this rate it is sometimes assumed that the population is subjected to exponential growth 3 during the period, and time is treated as a continuous variable. The size of an exponential population 4 would grow as an exponential function of time. The exponential growth rate 5 is equal to the instantaneous rate of growth 5. The ratio of natural increase (701-7) to the average population during a period is called the crude rate of natural increase 6 and is equal to the difference between the crude birth rate and the crude death rate. The vital index 7 is the ratio of the number of births to the number of deaths during a period; this measure is no longer much used.

  • 3. When time is treated as a discrete variable, reference is made to geometric growth.
  • 4. This is occasionally called a Malthusian population, but the term is ambiguous in view of its sociological connotations (see 906-1).