World Population Day

Population estimates.

  Looking at fertility and mortality trends is essential to understanding global demographic change . In the absence of migration (when the whole world is considered, net migration is zero), population growth refers to the difference between the number of births and the number of deaths . The births and deaths that took place over the past century determine the Current population size and composition . Population growth happens when there are more births than deaths. Over the past decades, there have been profound changes in birth rates, death rates, and population size globally. The number of births has been higher than the number of deaths. For example, in 1965, the crude birth rate (number of births per 1,000 population) was around 35, while the crude death rate (number of deaths per 1,000 population) was about 13. The difference was more than 20 per 1,000 population, and the rate of natural increase was 2 per 100 population (2%). The difference between crude birth rate and cr...

The demographic transition model is based on historical population trends of birth rates and death rates. The model explains typically how populations move from high birth and death rates to low birth and death rates through stages : Stage 1: High birth and death rates; population growth is slow. Stage 2: Death rates decline due to improvements in healthcare and sanitation; birth rates remain high, leading to rapid population growth. Stage 3: Birth rates begin to decline due to changes in societal values, increased access to contraception, and women's education. Stage 4: Both birth and death rates are low, stabilizing the population growth. Stage 5: In some models, birth rates fall below death rates, leading to population decline. The world has been going through the stages 2, 3, 4 and/or 5 of The demographic transition over the past 100 years.