ABSTRACT
The initial homeostatic demographic regime, in which high mortality necessitates high fertility to ensure the survival of the group, is overturned by economic and technological advances which induce a general decline in mortality rates. Infant and child mortality rates have been declining in the Petorca Valley for decades. Adult mortality rates for the Petorca Valley are even more difficult to establish with certainty than those of children because of the high number of adults lacking death dates and the wide span of years and ages to which adult deaths must be associated. The mortality transition in the Petorca Valley is associated with two major fluctuations in the fertility rate. The fertility transition in the Petorca Valley is only one aspect of the modernization process. The reality of the fertility transition is further substantiated by both the 1970 census manuscripts for the valley and the records of the local hospital.
