Number and Mean Age of Acceptors and Users as Related to Programme Duration.

The article presents a deterministic model designed to trace the consequences of the depletion of eligibles by previous acceptance when the other two factors, namely the age composition of parents and the disposition to accept among eligibles, are both held constant. Principal findings are that the decrease of eligibles by past acceptance can cause temporary declines in the number of new acceptors or current users, even when the disposition to accept among eligibles and the continuation rate among users are both held constant. Similarly, prior acceptance may alter the age composition of eligibles toward younger ages and by that means alone produce declines in the mean age of new acceptors and, more rarely, in the mean age of current users. Hence without further data one cannot legitimately infer an increased interest in spacing births as opposed to limiting their number merely from evidence of a decline in acceptors' ages. The article also says that a capacity to substitute an arbitrary initial age distribution for a stable one in order to allow for the fact that in many developing nations net migration or rapid mortality decline has or is about to increase the number of young parents relative to older parents, thereby intensifying at least temporarily the decline in acceptor's ages.