Abstract: The Chinese fertility rate has fallen to an extremely low level, with the decline in first-birth fertility constituting the primary driver of overall fertility reduction. It is increasingly essential to explore factors influencing the first-birth intentions of childless couples. Utilizing data from a specialized survey on never married groups, childless and single-child couples and employing a bivariate Probit model, this study examines how intergenerational coresidence influences the first-birth intentions of married childless couples. The findings reveal that coresidence with paternal parents significantly enhances husbands' and wives' first-birth intentions among both urban and rural couples, while coresidence with the maternal parents exerts a significant positive effect exclusively on urban couples. When coresidence stems from housing constraints, such arrangements partially counteract the positive impact of intergenerational coresidence on urban couples' fertility intentions. For rural couples living with paternal parents, couples' fertility intentions increase with husbands' share in marriage costs. These findings demonstrate the complex influence of intergenerational coresidence on couples' fertility intentions within the Chinese context, deepening our understanding of the interplay between family structure and reproductive decision-making. In light of persistent low fertility, fertility support policies should promote intergenerational support norms and provide targeted housing subsidies to alleviate structural constraints on childbearing.

Keywords: Motivations for Intergenerational Coresidence, Housing Constraints, Marriage Costs, Urban-Rural Differences, Gender Differences

摘要： 当前中国生育率已跌至极低水平，一孩生育率的下降成为主因，研究影响一孩生育意愿的因素具有重要的理论价值和政策意义。基于中国不婚不育少育群体专项调查数据，使用双变量Probit模型，分析代际同住对已婚未育夫妇一孩生育意愿的影响。研究发现，与丈夫父母同住会显著提升城乡夫妇的一孩生育意愿，但与妻子父母同住仅对城市夫妇的一孩生育意愿有促进作用;因住房条件限制而与父母同住会在一定程度上抵消代际同住对城市夫妇一孩生育意愿的积极作用;在农村从夫居家庭中，男方在结婚开支中所占比例越高，夫妇的一孩生育意愿越高。研究结果展现了在中国情境下代际同住对夫妇生育意愿的复杂影响，深化了对家庭结构和生育决策约束条件的认识。建议弘扬代际支持的传统文化，并为家庭发展提供住房支持。

关键词: 同住动机, 住房限制, 结婚开支, 城乡差异, 性别差异