Mortality Rate

Mortality rates provide information about deaths in a population. The most basic measure, crude death rate (CDR), is the number of deaths in a population per 1,000 individuals in that population in a given year. CDR is an inadequate, and sometimes misleading, descriptor of mortality because it obscures populations' age and sex structures. In order to understand who is dying and when, mortality rates need to be broken down into meaningful categories. Age, sex, cause of death, race/ethnicity, social relations, geographical factors, socioeconomic status, and human and environmental hazards can all influence levels of mortality. Due to age-specific patterns of mortality, age-specific and age-standardized rates are crucial to understanding populations' mortality profiles.

A typical age pattern begins with high mortality from birth to age 1, declining mortality from ages 1 to 5, mortality further decreasing from age 6 through late adolescence, and then mortality steadily climbing again through adulthood. This pattern makes the rates important: infant mortality rate (IMR < 1), child mortality rate (CMR 1–5), and 5-year age groups through the rest of the life course. The age pattern described is altered in high AIDS-prevalence populations, with a bump in mortality rates at prime ages (25–50), and a drop before climbing again at older ages.

While age-specific rates mirror CDR's computational structure, decomposing rates by age allows for more specific geographic and group comparisons. Age-standardized rates, on the other hand, compare mortality in one population to another by applying the age structure of Population A to the age-specific mortality rates of Population B, thus making evident where and how the age structure influences the overall level of mortality. Age-specific mortality rates make up one column of a life table, a central tool in demography, which allows mortality rates to be translated into a number of other measures, including the probability of surviving a certain age interval and life expectancy. Other important mortality rates include those that highlight specific causes of mortality; for instance, maternal mortality rate (MMR) captures the number of maternal deaths due to childbearing per 100,000 live births.

According to Population Reference Bureau statistics, in more developed countries CDR is 10/1,000, while less developed countries' CDR is 8/1,000. The larger percentage of older people, with a higher risk of dying in a given year, in more developed countries is what increases the CDR in these countries. When it is broken down, however, very different patterns emerge: IMR in more developed countries is 6/1,000, whereas it is 57/1,000 in less developed countries, and life expectancy at birth is 77 and 65, respectively. High HIV/AIDS prevalence leads to high IMR and low life expectancy (e.g., Swaziland: IMR 74/1,000, life expectancy 34 years). Important patterns also emerge when looking at racial/ ethnic and socioeconomic differences within developed country settings, with higher IMR and CMR among minorities and the poor. Such differences provide evidence for looking beyond CDR to mortality rates by age, cause, and sociocultural categories.