Life Expectancy at Birth
Definition
The average number of years a newborn infant would live if current mortality rates at each age remain constant throughout their life. It is the most widely used summary measure of population health.
Why It Matters
Life expectancy reflects overall health system quality, nutrition, sanitation, safety, and economic development. It is used to compare health outcomes across countries and track progress over time.
How It's Measured
Calculated from age-specific death rates using actuarial life tables. Published by the WHO, World Bank, and national statistics agencies.
Current Value
US: approximately 77.5 years; Japan (highest): approximately 84.8 years
Related Ranking
View ranking →Related Terms
Frequently Asked Questions
The average number of years a newborn infant would live if current mortality rates at each age remain constant throughout their life. It is the most widely used summary measure of population health.
Life expectancy reflects overall health system quality, nutrition, sanitation, safety, and economic development. It is used to compare health outcomes across countries and track progress over time.
Calculated from age-specific death rates using actuarial life tables. Published by the WHO, World Bank, and national statistics agencies.
this entity is one of the U.S. population demographics concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the the U.S. Census Bureau ACS and decennial files data behind every per-entity page on the site.
In the the U.S. Census Bureau ACS and decennial files data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.
Source: U.S. Census Bureau ACS, 2026.