Frailty index has been widely used to study the speed of change in frailty among older adults, and to depict the dynamic process of frailty caused by aging in recent years. Taking life course perspective as theoretical background, this study emphasizes the implications of observing and understanding the frailty trajectory within cohort, and also assumes that a framework for understanding the intra-cohort pattern of frailty should have three essential properties: random variability, trajectory heterogeneity, and cumulative disadvantage. Furthermore, relating these three properties to the specific parameters for growth curve models, datasets from China Longevity and Heath Longitudinal Survey is applied to test them. The primary results indicate that frailty trajectory follows a Ushaped curve, but there is significant betweenperson variation, and withingroup rather than between-group cumulative disadvantage mainly explains how the frailty trajectory differentiates.

Based on 2017 China Fertility Survey data, this paper analyzes fertility levels and trends over 2006-2016 in the ethnic minority provinces in China, using period and cohort measures of fertility incorporating quantity, structure and timing dimensions. The results show that the total fertility rate of ethnic minority provinces has increased to the replacement level in the past ten years, which is higher than the national average. The fertility rate of ethnic minority population is higher than that of the Han nationality, and this is the case at all parities. The secondchild fertility of Han has increased tremendously, highlighting the marked effects of the twochild policy. By ethnic group, the Uygur and Miao have strong fertility behaviors, meanwhile the Yi tends to have two children, while the Tibetans are reluctant to have more children. The fertility peak of ethnic minorities and Han women of childbearing age has been postponed from 20-24 years to 25-29 years, and the fertility level at the older age group of Han nationality has increased, pushing up the mean age at childbearing with that being higher of Han nationality than that of ethnic minorities. Overall, the ethnic minority provinces are at a moderately high fertility level.