Recovery time after a disaster and the ancient Maya

A simple demographic model is developed here that fits the observed data of population loss and recovery following a disaster. The model includes a constant annual growth factor and an immigration wave that is superimposed on it. The constant annual growth factor (∼0.3%) is modified by introducing the concept of Relative Attractiveness of the place under consideration. The model is sufficiently flexible to handle cases ranging from the fall/recovery of a major city, which occurs on a time frame of 10 years to the gradual deterioration and no recovery of a "doomed" society or some demographic effects of a sudden event such as the gold rush in California.The observed population recovery time data, which may spread over periods of centuries, include all the other processes at work in the recovering society, so that the parameters chosen for the model are averages over both time and demographic processes. The model enables the quantitative estimation of population recovery time given the relative population loss and estimated shape of the Relative Attractiveness function. The applicability of the model to various events of population decline and recovery throughout Maya history was demonstrated. It can be applied to the whole society or to specific Polities, provided the required data are available.Whenever the model is used, it has to be borne in mind that it is meant to provide rough estimates only, and that the original data, on which the model is based, have a considerable spread in them. Therefore, the appropriate spread has to be taken into consideration.Disasters, especially those that cause large population losses, in which the population recovery process includes an in-migration wave, can probably be observed in the archaeological records as "cultural transitions".