Using the census and sampling survey data between 1990 and 2020, this study examines the postponement of marriage and childbearing in China. The results show a persistent increase in the mean age at first marriage in urban and rural China. However, the postponement of the first marriage started earlier in urban areas than rural areas during 2000-2010. The postponement of first marriage in rural areas accelerated during 2010-2020. This led to a widening and then narrowing trend of the urban-rural gap. Age at first marriage differs across educational attainment; women and men with higher education significantly postpone their first marriage. Men with higher education also show a lower likelihood of staying unmarried for life. The curve of age-specific fertility rate for women at childbearing age has shifted downwards to the right, and the peak childbearing age of urban women has shifted more than that of rural women. The mean age at childbearing has been increasing, with a more rapid speed in 2000-2010 and then a slower one in 2010-2020. The mean age at childbearing of each parity has been postponed, especially for the first and second births. Women with different educational levels all postpone childbearing, and those with higher education levels show larger postponement.

Age structure is the most fundamental population structure, thus, assessing the accuracy of age reporting is an important prerequisite for census data usage. Using the data from population censuses and sample surveys, this paper employs the methods of comparing with other data sources, cohort survival ratio, modified Whipple index, and Sign Test to investigate the accuracy of age data in the 7th population census. The number of annual births estimated from population aged 0-9 in the 7th census and that releaseal by the National Bureau of Statistics are quite close, which preliminarily suggests that there is no obvious underreporting in the lowage group of the 7th census. The cohort survival ratios abnormally fluctuate in the age group of 10-40, reflecting the underreporting in the lowage group, the overreporting in youth group, and the larger overreporting of women of childbearing age than males in the 6th census. In addition, this study adopts the modified Whipple index and Sign Test method to examine the accuracy of age reporting in the 7th census. The results show that the 7th census age data is of high quality without obvious age heaping at the national level.

The number of older Internet users in urban China has increased rapidly in recent years, while the prevalence of Internet usage among older adults is still much smaller than developed countries. Using data from 2018 China Longitudinal Aging Social Survey, we find great gender, age, and education differences among the older adults in internet access, internet use, and ways of learning Internet. Older urban netizens use Internet frequently. Most of them use the Internet to socialize or search for information, while a small proportion of them try online shopping. Most of older urban netizens use mobile phones to get online. They learn about Internet use by themselves or asking for help from their family members rather than referring to resources outside household. The Internet use of older adults in urban China is largely affected by their individual attributes, family characteristics, socio-economic status, equipment and technical conditions, and their own interest in using smart devices. Based on these findings, we suggest that, to encourage the Internet use among older adults, producers should enhance the quality and types of services designed for older adults, and the community should play a more important role in promoting the Internet use among older adults.

Using the WPP2019 data, this article investigates negative population growth across the world during 1950-2018, and compares negative population growth between China and typical countries with identical origin point model. 107 countries (regions) in the world experienced negative population growth in 1950-2018, of which 20 were caused by the inherent mechanism of population. These 20 countries are all from Europe except Japan, and have experienced 19-year longest negative growth duration on average, and confront low fertility and population ageing. Compared to Germany, Hungary, and Russia, negative population growth occurs later in Japan and China, exhibiting a pattern of rapid development, long-term acceleration and weak resilience. In addition, the working-age population decrease earlier than the total population in Japan and China, ageing is severer, and the proportions of children aged 0-14 are lower. It is of growing significance to explore the new rules of population development, policy responses and long-term planning as soon as possible in the negative population growth era.

For thousands of years, the Chinese population has approximately been following exponential growth, with occasionally short-term exogenous decrease. In the 1990s, the intrinsic rate of natural increase turned negative, indicating the accumulation of negative population growth momentum. One quarter of prefecturelevel regions in China experienced negative population growth by 2010, as a result of population floating and migration. Population natural decrease was observed in 8% of county-level regions in China in 2010. According to the medium-variant population projection, China's population growth would become negative after 2027. The negative growth of working-age population would be much earlier and more rapidly than that of total population in the first half of this century. The older population would grow rapidly during this period. Negative population growth is not only a matter of quantity, but also of structure, which is directly affected by fertility, mortality and age structure changes. The mutually reinforcing process might happen between negative population growth and ageing. 

This study aims at investigating parenthood attitude toward adult children’s second birth under the“two-child”policy based on the Beijing Empty Nest Family Survey in 2015．The survey shows that the elderly present high awareness rate of the“two-child”policy; old parents who support，oppose to，or hold the idea of non-interference to their married children’s second birth account for one third re- spectively; almost 70% of the elderly would support their adult children’s second birth through economic assistance or child care; utilitarian purposes，such as old age care，are no longer primary reasons for second birth; economic cost，concern about mothers’or baby’s health and lack of child care resources become the top three factors preventing second birth．Having a good relationship with adult children， good health condition and being currently married have a significantly positive effect on parenthood support- ive attitudes toward adult children’s second birth; open-minded idea on endowment，education and duration of the empty nest period significantly reduce the probability of the elderly to support children’s second birth; and no significant effect is found with gender，age，economic condition and preferable place for old age life．

Fertility in China dropped below the replacement level in the early 1990s, and has been increasingly lower, arousing intense academic discussion on fertility policy adjustment．This paper estimates the size of objective population that is targeted by the two-child policy after computing the amount of the only children in 2012 based on the data of the 2005 national 1% population sampling survey, and analyzes its impact on number of annual births．The results show that on account of the large number of the objective population covered by the two-child policy and women's strong desire to have the second
child，if there was an immediate transition to a universal two-child policy, number of annual births would sharply increase with the peak value up to nearly 50 million and a total fertility rate of about 4.5．However, immediately implementing the two-child policy could significantly retard the negative growth trend of population in the future, increase labor supply and slow down population aging in China．

This article reviews the evolution of CPC leaders’ thinking on population issues during the Period of New Democratic Revolution and Socialist Construction.People are the subjects of social activities,and hence population theory is an essential part of the Marxist Theory.It has been a great concern of the CPC to apply Marxists’ population theory to investigate China’s population issues and explore the approaches of population development in the process of carrying out socialist revolution and constructions.In the early years of the CPC,its leaders criticized the viewpoint of "the overcrowding problem",which ensured the right direction of revolution.After the success of the revolution,the CPC has correctly recognized the law of population development,creatively put forward the notion of family planning,population control and accommodating population reproduction to material production.This has not only created a favorable population circumstance for the construction of socialism,but also made important contributions to the enrichment and development of Marxist population theory.