DEMOGRAPHY© Volume 20, Number 3 August 1983 POPULATION ESTIMATES FROM LONGITUDINAL RECORDS IN OTHERWISE DATA-DEFICIENT SETTINGS Douglas L. Anderton Department of Sociology, The University of Chicago, Chicago, Illinois 60637 Joseph Conaty Department of Sociology, The University of Utah, Salt Lake City, Utah 84112 Thomas W. Pullum Center for Studies in Demography and Ecology, University of Washington, Seattle, Washington 98195 Abstract-Existing methods for estimating population parameters in settings of data deficiency do not provide techniques for analysis of commonly available longitudinal data. In settings where complete population data is unavailable, longitudinal data recorded for only a subset of the total population are often available (e.g., event registers, genealogies). In this article we present and evaluate models which derive population parame- ters for the population subgroup underlying such longitudinal data. Using the distribution of individual times until first recorded event within a measurement interval, population parameters are estimated which provide basic denominator data for analyzing event occurrence. The models which we derive are especially suited to records which may include migration and population growth trends. The use of the models is demonstrated and evaluated through an application to genealogical records for a nineteenth- century population. Possible extensions of these models and their major limitations are also discussed. Established methods for estimating population parameters rely upon specific demographic records and do not fully exploit other, often more commonly available, data sources for human popu- lations. Population estimation tech- niques designed for data-deficient set- tings are based upon survivorship calculations and require the use of cross- sectional population enumerations in ad- dition to longitudinal vital event registra- tions or model life tables (Brass and Coale, 1968; Coale and Zelnik, 1963; Preston and Hill, 1980). The existing methods which use only longitudinal reg- istration data assume registration com- pleteness and population closure (Lee, 1977). In addition, these methods esti- mate only total population parameters rather than population subgroups and do not provide basic denominator data for analyzing recorded events. An attractive alternative to these methods would esti- mate open population parameters for un- derlying subgroups solely from longitudi- nal records in data-deficient settings. In addition to the demographic registrations used by the methods above, there are numerous records which are left behind during the individual's life cycle. Thus, within the context of this paper, data- deficient refers not to a lack of recorded information on individuals but to the lack of reliable cross-sectional enumerations for subgroups of interest. In this sense, many commonplace demographic set- tings are data-deficient. For example, vital statistics registration records may be used to estimate fecund women in a population while no cross-sectional enu- 273