Construction of expanded infant life tables: A method based on a new mortality law

A mortality law for infants is developed for constructing augmented-period infant life tables. For advanced countries, the three-parameter model is found to fit the mortality data for subdivisions of the first year of life extremely well, with estimates of the life-table functions calculated from the proposed model closely matching those constructed by the traditional method. Thus, considerable benefit is derived by replacing a large accumulation of data, marred by inevitable irregularities and errors arising from incomplete reporting and other sources, with a simple formula that can produce life-table functions at any age point and for any age interval and can be handled with some facility. We have also demonstrated how the model is used to calculate a number of new life-table functions and parameters of the lifetime distribution with their attendant applications, which include determination of the maximum life expectancy and the force of mortality at birth as well as certain average lifetimes for the stationary population. It is found that over 97% of the information contained in an augmented infant life table can be summarized by three parameters, with the remaining portion captured by another three parameters.