3333glossary    * R *
Demographical and statistical terms Symbols
rate computation
the crude birth, death, marriage, divorce etc. are generally the annual number of each of these vital per 1000 mid-year population. 		 
rate of population growth
the increase or decrease of a population in a period divided by the number of person-years lived by the population during the same period. 		r or TA
rate of natural increase at time t, or b(t)-d(t)
the difference between the births and deaths occurring during by the number of person-years lived by the population during the same period. This rate, which specifically excludes changes resulting from migration, is the difference between the crude birth rate and the crude death rate. 		n(t)
replacement-level fertility
the level of fertility at which a cohort of women on the average are having only enough daughters to replace themselves in the population. By definition, replacement level is equal to a net reproduction rate of 1.0. The total fertility rate is also used to indicate replacement-level fertility. Generally, in industrialized countries, a TFR (total fertility rate) of 2.1 is considered to be replacement level. 		 
reproductive histories
are accounts obtained for individual women of the important events in their reproductive lives, such as marriages, pregnancies, births, infant deaths, etc., and their dates. Reproductive histories are often obtained retrospectively from surveys. 		 
resistance function
is the mathematical expression of the resistance data computed on the life-table. 		r(x);

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