Sex ratio of population (women per 100 men)
Projections of the total population and population by sex are prepared by the Population Division of the United Nations Secretariat and revised every two years in order to incorporate new data. The preparation of projections involves two distinct processes: (a) the incorporation of all relevant information regarding past demographic dynamics of the population of each country or area of the world; and (b) the formulation of detailed assumptions about the future paths of fertility, mortality, and international migration.
The medium variant projections for 2007 refer to 1 July of the given year and assume the following: Total fertility in all countries eventually converges toward a level of 1.85 children per woman by the end of the projection period (2005-2050). However, not all countries reach this level during the projection period. The basic principle of the fertility projection is the same for all countries, but projection procedures are slightly different depending on whether countries had a total fertility above or below 1.85 children per woman in 2000-2005. Mortality is projected on the basis of models of change of life expectancy that produce smaller gains the higher the life expectancy already reached. The selection of the model for each country is based on recent trends in life expectancy by sex. For the 60 countries highly affected by the HIV/AIDS epidemic, estimates of the impact of HIV/AIDS are made by explicitly modeling the course of the epidemic and by projecting the yearly incidence of HIV infection. International migration is projected on the basis of past international migration estimates and an assessment of the policy stance of countries with regard to future international migration flows.
In the case of official national statistics compiled through the Demographic Yearbook system, the total, female and male population refer to the population enumerated at the most recent census for which data are available.
The sex ratio is calculated as the number of females per 100 males.
(Source: United Nations Statistics Division)