The four-parameter logit life table system

Summary Brass's model life table system, which is a two parameter system based on the logit transformation of survivorship values, has been widely and successfully used to describe age patterns of mortality in many populations. As more reliable information has become available for populations with mortality patterns which differ in important ways from the assumed standard pattern of mortality, a more flexible model system is needed. This paper shows how Brass's system can be expanded into a four-parameter model, and evaluates the performance of the new system by examining how well it can fit observed life table data.     

The Decline of marital fertility in Japan

Summary Studies concerning the demographic history of Tokuwara and Meiji Japan suggest that fertility rose substantially before declining during the twentieth century. Were the motivations and circumstances which held down natality during the feudal period similar to those which account for the modern fertility decline and the low birth rate obtaining in the Japan of to-day? The thesis of this paper is that the pre-modern situation was fundamentally different from the modern one. During the Tokugawa era infanticide and abortion were used, independently of parity, to eliminate weak offspring whose chances of survival were deemed poor. Desired natality generally exceeded natural fertility. With the rise of income per head during the Meiji period the population's need for these desparate practices vanished. To-day parity-specific control characterizes fertility. Parityspecific control was diffused throughout Japan in response to declining desired fertility. Desired fertility fell significantly below natural fertility sometime during the late nineteenth or early twentieth century and the wish to reduce actual fertility to the desired level stimulated the adoption of parity-specific control. The speed of decline in marital fertility was partially governed by official policies toward contraception and abortion, contraception and abortion.     

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