Life Expectancy: Definition & Calculations

Instructor: Angie Generose
Life expectancy for a person in Western Europe is dramatically different than it is for a person in rural Africa. Learn about factors such as nationality that affect the length of one's life and explore how this figure is calculated.

Life Expectancy Definition

Life expectancy refers to a prediction of the number of years for which a person will live. This number is determined based on the statistical average, considering many factors, including year and place of birth, race, education level, income, and medical history. There are many different types of life expectancy calculations, and the number varies over time. For instance, according to Galor and Moav (2005), the life expectancy during the Bronze Age was 26 years, while a baby born today in the United States can expect to live 78.88 years.

Factors Affecting Life Expectancy


One of the most significant factors in determining one's life expectancy is his place of birth. The Central Intelligence Agency (2014) reports that currently, the small country of Monaco in Western Europe has the longest life expectancy at 89.52 years. This is due to factors including a strong healthcare system with access to services for all citizens, high average income, a healthy Mediterranean-style diet, and a low infant mortality rate. Conversely, South Africa has the lowest life expectancy at 49.72 years. This is due to poor living conditions, limited access to high quality medical care, and the HIV/AIDS epidemic.

See the following map to see how life expectancy varies across the world:

Life Expectancy Map


Your race/ethnicity also plays a big role in determining life expectancy. For instance, according to the Center for Disease Control (2014), in the United States, the life expectancy is 78.9 for White Caucasians, 74.6 for African-Americans, 82.8 for Latinos, 86.5 for Asian Americans, and 76.9 for Native Americans. Fortunately, these disparities have been decreasing over recent decades. The 4.3-year gap in life expectancy between White Caucasians and African-Americans is near the lowest it has been since 1975.

Infant Mortality and Years Lived

Because life expectancy is a statistical measurement, it is affected by outlier events such as high infant mortality rates. The U.S. Department of Health and Human Services reports that Native Americans have an infant mortality rate of 6.9 per 1000 births, which is more than twice the rate for Caucasians. Even if the members of the two populations lived to the same average age, the life expectancy of Native Americans would be lower due to the infant mortality rate. Therefore, the actual number of years in a person's life can be much higher or lower than the life expectancy rate.

As one gets older, his overall life expectancy increases because the chances of outlying factors of early death, such as infant mortality, are reduced. In other words, the longer a person has lived, the longer his life expectancy will be. Therefore, with all other factors being equal, a person who is 50 years old will have a higher life expectancy than a person who is 25.

Additional Factors

Additional factors that will increase one's life expectancy are being female, being in the top 50% income bracket, holding a college degree, maintaining a healthy medical history, and having a healthy family medical history. The choices that one makes will also affect his life expectancy. Life expectancy is higher for those who eat healthy food, exercise regularly, and avoid alcohol, tobacco, and drugs. It's also higher for those who do not engage in risky behavior such as drinking and driving.


Mathematical Terms

Life expectancy can be represented in mathematical terms as ex, in which e is the number of years remaining in a person's life, and x is the number of years a person has already lived. This is a common method that researchers and mathematicians use to represent life expectancy. For instance, if a person's life expectancy is 80 years, and he is currently 30 years, his life expectancy would be represented as 50/30.

Calculating Your Life Expectancy

Complete the activity below to calculate your life expectancy. Keep in mind that this is an imprecise calculation, as life expectancy is extremely unpredictable on an individual level. These questions are typical of life expectancy calculators; however, this list is not exhaustive, as there are hundreds of factors that would affect a true life expectancy calculator. This activity is designed for individuals living in the United States.

• Begin at 74 years old.

• Add six years if you are female.

• If you are 50 or older, add ten years.

• If two or more of your grandparents lived to at least 80 years, add five years.

• Subtract two years if an immediate family member (parent, grandparent, sister, or brother) died of a heart attack, stroke, or cancer before the age of 60. Subtract an additional two years if they died before the age of 50. Only make these subtractions once, even if this statement is true for more than one immediate family member.

• Subtract three years for EACH case of diabetes, thyroid disorder, breast cancer, cancer of the digestive system, asthma, or chronic bronchitis within your immediate family.

• Subtract five years if you currently have a moderate or severe case of a disease or disorder such as cancer, diabetes, epilepsy, gallbladder disease, heart disease, hypertension, or chronic obstructive pulmonary disease.

• If you are married, add four years.

• Add two years if your family income is over $60,000 per year.

• Subtract three years if you have lived at the poverty level for at least 50% of your life.

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