Based on the analysis of national birth monitoring data, this paper suggests that declining number of births in recent years in China is driven jointly by the reduction of births among women aged below 30, the decrease of first births and the waning growth of the second births. The outbreak of COVID-19 further drastically depressed the number of births among women aged below 30 and reduced the number of first births in the fourth quarter of 2020, resulting in an accelerated decline in the number of births in 2020.

There has been an agreement among international communities that social participation of the elderly people can actively cope with the issue of population ageing.However,most of the previous studies mainly focus on how social participation affecting health,little attention has been paid to the bi-directional relationship between the.Using the data of the Chinese Longitudinal Healthy Longevity Survey ( CLHLS) ,this paper explores this question using the logit and fixed effect models.After controlling for confounding factors,the model results show that there does exist significant bi-directional relationship between self-report health ( SRH) and social participation of the Chinese elderly.It is suggested that those older adults who report good SRH have a 22.0% ～ 40.1% higher odds ratio of engaging in social participation than those who have poor SRH; older adults who are engaged in social participation have a 16.4% ～ 25.6% higher odds ratio of reporting good SRH; the influence of SRH on social participation might be larger than that of social participation on SRH．Besides,the results reveal that the impact of social participation on SRH is more effective among elderly who report good SRH at baseline．