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Multilingual Demographic Dictionary, second unified edition, English volume

Period of observation

Multilingual Demographic Dictionary, second unified edition, English vol.
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Period of observation  (PERIOD of observation)


Demographic indices (132-7) will in most cases relate to a particular period of observation 1 ; this is true in particular of most rates (cf. 133-4). An annual rate 2 will relate to a period of twelve months. Where observations are collected for a number of years and then averaged, the term mean annual rate 3 or average annual rate 3 is often used for the result. Where rates are calculated for periods different from a year they are converted to an annual basis 4 through multiplication by an appropriate factor. Instantaneous rates 5 are sometimes computed; they relate to an infinitesimal period of time, cf. for instance the instantaneous death rate (431-4) or the instantaneous rate of population growth (702-5). More...