ABSTRACT
In this chapter, we introduce demographic systems and demographic accounts.
A demographic system includes a set of membership criteria that mark out the population of interest; a classification scheme distinguishing between different groups within the population of interest; ways of entering or exiting the system; and movements between statuses.
A demographic account is a collection of linked demographic arrays describing a demographic system. A demographic account includes an array of population counts, plus one or more arrays of counts of events. Every sub population within a demographic account must conform to a fundamental accounting identity: population at the end of each period equals population at the beginning of the period, plus entries during the period, and minus exits during the period.
We illustrate the construction of demographic accounts using the population of 12 fictitious individuals. We construct an account with no region and no age, an account with region but not age, and an account with age but not region.
We then present two optional sections: one discussing the difference between movements accounts and transitions accounts, and the other giving a mathematical description of the demographic accounting identities for movements accounts.
