ABSTRACT
The core of the Ecesis demographic model is an interregional cohort-component accounts model. In principle, demographic accounting is similar to double-entry bookkeeping; for a given period, total debits must equal total credits. The units of account are people and debits are outflows from the population and credits are inflows into the population. The process is complicated, but essentially unchanged, when age, sex and racial detail are added to the populations. As another example, the population at-risk of giving birth in a state should include women of childbearing age who migrate into a state. Migrating women who survive will appear, on average, in the at-risk population of both the origin and destination states for half of the time period. The version of the Rees-Wilson model used in ECESIS is modified to use gross in- and outmigration totals rather than place-to-place flows.
