A multiregional model for regional demographic projection

This chapter presents a new model for regional demographic projections in the Netherlands; the model projects the population of all regions simultaneously. This multiregional approach combines the advantages of a top-down approach with those of a bottom-up approach. The major features of the model are: 1) it is purely demographic 2) it is two-sex and female dominant 3) the lengths of age intervals are free but equal to length of unit profection periods 4) the number of regions is free 5) external migration is taken into account 6) it is deterministic 7) it is time discrete 8) it is aware of model paramenters and 9) model structure and estimators of the parameters are derived from a set of accounting equations. The model distinguishes between prospective and retrospective observations. An observation is prospective if the demographic events experienced by members of a cohort are recorded as they occur; an observation is retrospective if the events are recorded some time after occurrence. The fundamental parameters of the projection model are occurrence and exposure rates; they are ratios of the number of events of a given type that occur in a particular observation interval by the persons at risk of experiencing that event. The estimator of the occurrence and exposure rates together with the flow or accounting equations determine the projection model equations and generate estimates of the transition probabilities. The period-cohort observational plan implies that all events for a certain year are recorded according to year of birth of the person or equivalently according to age at the beginning or at the end of the observation interval. Overall it is asserted that the period-cohort observational plan is most appropriate for projection purposes.