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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