Indian Population Decline: The Missions of Northwestern New Spain, 1687-1840

The central finding is that diseases are only part of the explanation of population decline. In addition to deaths due to such illnesses as measles and smallpox and to psychological trauma, we must consider the effects of declining fertility among Indian women manifested in abortions, miscarriages, and death in childbirth. Moreover, the unhealthy conditions in missions often resulted in nine of ten children dying before age eight.