A probability model for closed birth interval to study the effect of migration on fertility
by
S. N. Singh
University of Transkei, SOUTH AFRICA

A number of probability models have been developed to study the fertility behaviour of migrated couples mostly based on the number of births during a specied period of time. BUT very fiew models relating to birth interval data have been developed so far to study the fertility of migrated couples which is more sensitive index for detecting current chenges in fertility pattern of women who are still in reproductive ages than the number of births (Pathak 1971, Chakraborty 1976, Pathak,et al 1993). The objective of the present study is to derive a Probability Model to describe the variation in the length of any order of closed birth interval of females of large marital duration with the assumption that the fecundability for females of migrated and nonmigrated couples is different and remains constant till the next birth. While deriving the model variation in the length of PPAhas also been considered. The model has been further extended by allowing variation in the length of PPA and is presented in SECTION 2.

In SECTION 3, the model has been illustrated with a set of observed data and the estimate of fecundability is obtained.

Date received: August 24, 2000