Concubinage and the quantity–quality trade-off in Qing China: using genealogy data, 1636–1912

The quantity-quality trade-off theory posits that higher fertility can dilute investment in each child and weaken status attainment. Yet most research has examined this mechanism at the individual or household level, leaving its operation within hierarchical and historically embedded lineage institutions underexplored. This paper situates the quantity-quality trade-off within Qing Chinese lineage institutions, where material resources, educational opportunities, political access, and symbolic status were unevenly distributed across households and generations. Using published genealogical statistics for 40 lineages, we construct a dataset with the lineage-generation as the unit of analysis. Both OLS and Lewbel IV estimates show a negative association between birth density and lineage social status. Quantile regression reveals that this relationship was stratified. Birth density was positively associated with lineage status at the 20th and 30th conditional quantiles and negatively associated with status at the 90th percentile. Mechanism analyses demonstrate that this relationship was deeply shaped by the internal hierarchy of the lineage, which depended on maternal status. Wife fertility did not significantly change the negative effect of birth density, whereas concubine fertility weakened it. The negative effect of birth density declined as concubine fertility increased. The analysis of reproductive structure also links higher birth density to concubine-related fertility in the full model. Heterogeneity analyses further show that this buffering pattern was most visible among lower-status lineages and during the High Qing period. These findings extend the empirical application of the quantity–quality framework to Qing lineages, showing how the relationship between fertility and status varied with social position and reproductive hierarchy.