Our study has important limitations. First, it used the methods of observational research, which means that we cannot be certain that changes after the introduction of national health insurance were due to national health insurance. Second, more than half (57%) of the population had medical insurance at the start of national health insurance, which may have diluted the effect of national health insurance, although those who gained insurance were mainly the elderly and the vulnerable, many of whom were in the least healthy health class groups. Third, in some instances, we did not have similar data before and after the introduction of national health insurance to adjust for the possible effects of unrelated social changes on life expectancy. For example, social changes, such as the helmet law for mortorcyclists, probably improved life expectancy. Fourth, quality of care after the introduction of national health insurance varied across health class groups: Higher-ranked health class groups were primarily found in urban areas, which have superior health care facilities (49). Fifth, life expectancy is an imperfect health indicator. It is widely used and easily understood (20) but not sufficiently sensitive to the effect of specific causes of deaths, forcing us to use analytic methods that assume that causes of death are independent of one another. In addition, income, education, and the environment all contribute to life expectancy, and the contribution of access to health care in Taiwan to improvements in life expectancy is unknown. Therefore, using life expectancy as a summary measure may miss effects of improved access to care due to national health insurance. Sixth, the value of national health insurance goes far beyond prolongation of life, which is the only indicator of health in this study. It can relieve pain and suffering, improve quality of life, provide emotional security, and increase human dignity. Finally, a 10-year period may be too brief to measure the full effect of national health insurance. However, this shortcoming is partially offset by comparing the period after the introduction of national health insurance with an additional 10 years before its introduction.