9Bernheim,B. D. ,L. Forni,J. Gokhale,and L. J. Kotlikoff. The mismatch between life insurance holdings and financial vulnerabilities: Evidence from the health and retirement study [ J ]. American Economic Review, 2003,93:354 - 365.
10Cragg, J. G. Some statistical models for limited dependent variables with application to the demand for durable goods [ J ]. Econometrica, 1971,39 : 829 - 844.