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The world’s population continues to grow, reaching 7.8 billion by mid-2020, rising from 7 billion in 2010, 6 billion in 1998, and 5 billion in 1986. The average annual growth rate was around 1.1% in 2015–2020, which steadily decreased after it peaked at 2.3% in the late 1960s. Among 201 countries and areas, 73 countries had a smaller growth rate in 2010–2020 compared with the previous decade; and out of these 73 countries, more than 60 are developing countries. The slowing pace of the population growth is closely related to declines in fertility. Globally, the total fertility rate was 2.4 births per woman of reproductive age in 2020, decreasing from 2.7 in 2000, 3.7 in 1980, and 5.0 in 1950. In high-income and upper-middle-income countries, the total fertility rate has been below replacement level (2.1 births per woman) for a few decades, which is the level required to ensure the replacement of generations in low-mortality countries. In a few of these countries, total fertility rates have even fallen to extremely low levels, 1.5 births per woman, and even below 1.5 in some countries, for the past several decades.
There is a myriad of reasons for the slowing pace of population growth that can be attributed to declining fertility in the context of a demographic transition mainly caused by modernization. In the process of modernization, improved food security, nutrition, and public health, advances in medical technology and socioeconomic development, coupled with improved safe and effective family planning methods and services have largely improved child survival, which has enabled couples to have a desired number of children without having too many births. Improved education, enhanced women’s empowerment, increased financial security in old age, and personal aspirations for more opportunities regarding self-career development and a better life have all reshaped young couples’ views and behaviors about postponements of marriage and childbearing, and the numbers and timing of childbirths (2-3). All of these forces have led to reductions in fertility, and eventually triggered a demographic transition. By 2020, all countries and areas either have completed their demographic transition or are in the middle of the transition.
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