World Population Day (WPD) was established by the United Nations (UN) in 1989 and celebrated annually on July 11 (1). The aim of celebrating WPD is to overcome urgent and important population issues and to raise the awareness of the public. While many countries face challenges of rapid population growth, other countries such as China are experiencing a reduction in population size and facing the challenges of a falling proportion of working-age population, population ageing, urbanization, and population migration (2). Compared with 2017, China’s total number of births has decreased by 2.58 million in 2019 (3), and the total population is projected to decrease by 31.4 million (2.2%) between 2019 and 2050 (2). Moreover, China is currently the only country in the world with an elderly population of more than 200 million, and the migrant population has reached 236 million in 2019 (4). The above population issues are closely interrelated with the 2030 Sustainable Development Goals (SDGs) put forth by the UN. Therefore, in order to achieve the world blueprint of sustainable development, we must understand and overcome these population issues.
The theme of the coming 31st WPD in 2020 will be “Putting the brakes on COVID-19: how to safeguard the health and rights of women and girls now” (5). This theme aims to raise awareness about the sexual and reproductive health needs and vulnerabilities of women and girls during the pandemic and to explore how to maintain the momentum towards achieving the SDGs by 2030.