Mortality Rate

The crude mortality rate refers to the incidence of death per 1,000 people among a given population and is thus essentially the same as the crude death rate; it is therefore closely linked to life expectancy. Mortality should not be confused with morbidity, the incidence or prevalence of a given disease. Demographers typically rely on age-specific and sex-specific mortality rates, which measure the number of deaths of a given 5-year age group of males or females. Mortality rates vary considerably across the life cycle, depending on the particular social circumstances in which people live. Typically, mortality rates tend to be relatively high for infants (especially in economically underdeveloped societies) and low during childhood and young adulthood, and then they rise steadily as a person enters middle age, increasing dramatically in old age. However, mortality is a complex phenomenon with multiple demographic, economic, sociological, psychological, cultural, and geographic dimensions.

Like fertility, mortality is a reflection of both biological circumstances (e.g., genetics, diet) and socio-environmental context. The causes of mortality vary greatly among societies (as well as within them). Infant mortality rates (number of deaths of babies less than 1 year old per 1,000 infants) are an important measure of a society's health, as infants are the most vulnerable members of any society. Typically, infant mortality rates are high in preindustrial societies, both historically and in the present; in much of sub-Saharan Africa, infant mortality rates exceed 120 per 1,000 babies. In contrast, economically developed regions such as North America, Japan, and Europe have infant mortality rates of less than 25 per 1,000.

In preindustrial social contexts, the leading causes of mortality are generally infectious bacterial (and to a lesser extent, viral) diseases, including, among others, respiratory infections (e.g., pneumonia), diarrheal diseases (e.g., dysentery), cholera, malaria, tuberculosis, and measles; today, that list also includes AIDS. Many of these diseases are waterborne. Thus, crude mortality rates in much of the developing world (Latin America, Africa, the Middle East, and Asia excluding Japan) tend to exceed 20 deaths per 1,000 people annually. As societies industrialize, the mechanization of agriculture and the correspondingly lower prices of food tend to improve diets and thus lower mortality rates and raise life expectancies. Improved public health measures (particularly, clean drinking water) and access to health care are also important. Thus, crude mortality rates in Europe, Japan, and North America are generally less than 7 deaths per 1,000 people annually. These changes are an integral part of the demographic transition that commonly accompanies industrialization.

Moreover, the decline in mortality rates is accompanied by a shift in the causes of mortality, a phenomenon often called the “epidemiological transition.” Essentially, mortality in economically advanced societies tends to result from environmental and behavioral causes, including obesity, smoking, and alcohol use, which produce proximate causes of death such as heart disease, strokes, and various forms of cancer. Excluding the middle aged and the elderly, other important causes include automobile accidents, homicide, suicide, overuse of prescription medications, illegal drug use, and household accidents.