From The World Bank Group Methodology
Population Projection technical notes
Population projection tables provide population estimates and projections for nearly
200 economies. The input data used for the projections include a base year (mid-1995)
population estimate by age and sex, and base period (1995-00) estimates of mortality,
fertility and migration. For further information on the projections methodology see Eduard
Bos and others, World Population Projections 1994-95, Johns Hopkins University Press,
Baltimore, MD, 1994.
Population is a World Bank estimate for mid-year population, based, in
most cases, on a de facto definition, which counts all residents regardless of legal
status or citizenship. Note, however, that refugees not permanently settled in the country
of asylum are generally considered to be part of the population of their country of
origin. Population numbers are either current census data or historical census data
extrapolated through certain demographic models. The average annual growth rate
is computed from end-point data using an exponential growth model. The equation is r
= ln(pn/p1)/n where pn and p1
are the last and first observations in the period, n is the number of years in the
period, and ln is the natural logarithm operator.
Birth rate and death rate indicate the number of live
births and the number of deaths occurring per year per 1,000 midyear population. The
difference between birth and death rates is the rate of natural increase
(expressed in this table as per 100).
Net migration rate is the difference between immigration and emigration
per thousand population.
Total fertility rate represents the number of children that would be born
to a woman if she were to live to the end of her childbearing years and bear children in
accordance with prevailing age-specific fertility rates.
Net reproduction rate (which measures the number of daughters a woman
will bear during her lifetime, assuming fixed age-specific fertility and mortality rates)
reflects the extent to which a cohort of girls will reproduce themselves.
Life expectancy at birth indicates the number of years a newborn infant
would live if prevailing patterns of mortality at the time of its birth were to stay the
same throughout its life.
Life expectancy at age 15 indicates the number of years a 15 year-old
would live if prevailing patterns of mortality were to stay the same throughout its life.
Infant mortality is the number of infants who die before reaching one
year of age, per 1,000 live births in a given year.
Under 5 mortality is the probability that a new born will die before
reaching age 5, if subject to current age-specific mortality rates.
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