The project develops improved hazard rate models for analysis of the occurrence of two or more life events, such as (1) death by different causes, (2) marriage and cohabitation, (3) marital childbirth and voluntary job separation among employed women, or (4) initiation and relapse of different types of illicit drugs whose risks are not independent. These models distinguish two types of risk interdependence by extending existing models for the analysis of such competing events. One type is due to a direct interdependence of hazards such as risk interdependence which exists when an increase in the risk of a particular cause of death increases the risk of other causes of death, and vice versa. The other is due to unobserved individual differences such as risk interdependence which exists when a person who has a certain unmeasured morbidity is at higher risk of multiple causes of death. Existing models for analysis of competing events known as correlated frailty models consider mainly the latter and not the former type of risk interdependence, while the current project will develop models to account for both types. This project will also develop "causal models" for analysis of the influence of an event on the occurrence of another event, such as the influence of premarital cohabitation on marriage, or the influence of initiation of marijuana on initiation of other illicit drugs. The risk interdependence between two life events generates non-randomness of people who experience the first event regarding the risk of the second event. By taking into account the two aspects of risk interdependence, the new models can assess the causal effect of experiencing the first event on the occurrence of the second event by eliminating bias in the selection of people into the experience of the first event.
This research will thus contribute to a deeper understanding of interdependence among life events. It will also provide better causal analyses regarding the possible influence of a life event on the likelihood of occurrence of another event. In particular, the project will analyze the interdependence between marital childbirth and voluntary job separation among employed women in Japan in order to study how differences in family-friendliness of the workplace affect the relationship between these two life events.
