tailieunhanh - Analysis of Survey Data phần 8

Điều này phù hợp với những phát hiện của Altonji và Segal (1996). Bằng chứng này cho thấy rằng nó là an toàn hơn để chỉ định V là ma trận nhận dạng và sử dụng Rao ± Scott điều chỉnh để thử nghiệm. | ESTIMATION RESULTS 259 destination-specific Gamma heterogeneity uncorrelated across spells. Second the transition intensities are not generally monotonic an increasing then falling pattern is found for the transitions C YTS E YTS and YTS U. The aggregate hazard rate is non-monotonic for exits from college employment and unemployment. Third transition intensities for exit to college are very small for all states of origin except unemployment where there is a sizeable intensity of transition into education at short unemployment durations. The generally low degree of transition into state C reflects the fact that for most people formal post-16 education is a state entered as first destination after leaving school or not at all. However the fact that there are unobservables common to both the initial state and transition parts of the model implies that the decision to enter college after school is endogenous and cannot be modelled separately from the transitions among the other three states. The discontinuity of exit probabilities of the two-year YTS limit is very marked see Figure . Figure shows the aggregated hazard rates xk t x u 2 ci governing exits from each state of origin k. The typical short unemployment duration-simply a high hazard rate for exits from unemployment but declining strongly with duration implying a heavy right hand tail for the distribution of unemployment durations. For the other three states of origin the hazard rates are rather flatter except for the one- and two-year peaks for college spells. Note that we cannot distinguish unambiguously between true duration dependence and the effects of non-persistent heterogeneity here at least not without imposing restrictions such as proportionality of hazards. . Simulation strategy The model structure is sufficiently complex that it is difficult to interpret the parameter estimates directly. Instead we use simple illustrative simulations to bring out the economic implications of the .