World Population Day is observed annually on July 11th to enhance awareness of population trends, including the impact on a large array of development challenges.
It is estimated that there are about 8.2 billion people on this planet in 2025. The world population was about 3 billion in 1960 and grew to 8.2 billion in 65 years. According to the projections by the United Nations, it is likely that the world population will continue to grow and reach 9.6 billion in 2050.
Fertility and mortality trends
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 crude death rate was larger than 10 per 1,000 population until 2019, which contributed to population growth, but this difference has been steadily shrinking.
The demographic transition model
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.
Declining fertility rates
The number of births is determined by two key factors: the number of women in their reproductive age and the average number of children those women have (total fertility rate, TFR). Globally, total fertility rates started to decline in the 1960s. Factors contributing to this decline include:
- Increased access to education, particularly for women.
- Economic factors, such as the cost of raising children.
- Shifts in societal norms and values regarding family size.
Regional variations
Fertility trends vary significantly across different regions of the world. Currently, the Sub-Saharan Africa region has the highest total fertility rates in the world. Despite some decline in recent years, the average number of children a woman was 4.3 children in 2023, higher than other regions. Total fertility rates in Europe and Central Asia, and in North America, have been among the lowest globally since 1960, and it was 1.6 children on average, in 2023. In other regions, total fertility rates were high in the 1960s but have sharply declined since. Fertility decline in East Asia and Pacific was drastic, and the fertility rate was lowest (1.3 children on average) in 2023.
Variations at the economy level
Currently, economies across the world are in different phases of demographic transition, and total fertility rates vary significantly. Fertility decline is particularly pronounced in some places, where total fertility rates have fallen below the replacement level of 2.1 children per woman (the replacement level fertility is the average number of children per woman needed to maintain a stable population size). In 2023, in seven economies, on average, a woman gave birth to less than one child. On the other hand, there were five economies where, on average, a woman gave birth to more than six children. These economies with fertility rates higher than six were all in the Sub-Saharan Africa region.
Age distribution of population and population aging
Not only the size of the total population but the age composition of the population is crucial for understanding societal needs. Changes in fertility and mortality rates significantly alter a population’s age distribution. As fertility rates decline and mortality rates decrease (e.g., an increase in life expectancy), populations as a whole tend to age.
Europe and Central Asia and North America are experiencing population aging. In both regions the proportion of people aged 65 and older is around 18%, and the proportion of people aged 0-14 at 17%. In contrast, Sub-Saharan Africa has the youngest population, with 40% of people aged 0-14 and only 3% aged 65 and above.
In conclusion, these demographic changes herald significant shifts in population dynamics. Global population has grown substantially over the past decades, driven by relatively high birth rates and low death rates. The demographic transition model explains the stages of population growth and decline, with some economies experiencing declining fertility rates and aging populations, while some others still experience high fertility and rapid population growth.
Regional variations in fertility rates and age distribution underscore the diverse demographic situations faced by different economies. World Population Day is an opportunity to recognize the impact of these trends, and to create strategies address the challenges and opportunities they present, for a sustainable future.
These population and demographic figures at global, regional and economy levels are produced and available on the World Population Prospects database by the United Nations Population Division, the Population Estimates and Projections database and the World Development Indicators database by the World Bank.
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