The area comprising Pakistan has had a long history of regular census taking. Registration of births and deaths is also obligatory in a number of political units especially urban areas1. In addition, a number of sample surveys have been carried out to determine various characteristics of the population of Pakistan. However, it remains a fact that we do not know enough about such important factors as the birth and death rates of the population. Even the total size of the population, not to speak of its age and sex distribution, is a debated figure. A number of attempts have been made to arrive at reasonable estimates of this ‘true’ figure for the total size of the population, its age and sex distribution as well as of the vital rates employing different techniques. Some of most-quoted ones include those by Ahmad [4, p. 44], Khan and Ziauddin , Krotki [6, p. 291], and Zelnik and Khan .