Final answer:
Life expectancy is the statistical measure of the average lifespan an individual is expected to live based on the year of their birth, gender, and other factors, which is influenced by conditions like healthcare and socio-economic factors.
Step-by-step explanation:
Life expectancy refers to the average number of years that an individual is expected to live from the time of his or her birth. It serves as a statistical measure that reflects the average age of death within a population, varying by birth year, gender, and other factors. Life expectancy is influenced by a myriad of factors such as nutrition, healthcare, sanitation, exercise, as well as external factors such as epidemics, wars, and natural disasters.
In developed countries like the United States, life expectancy has significantly increased, where males born in 2015 have a life expectancy of about 77 years and females about 82 years. With continual improvements in health care and living conditions, a growing number of individuals are living beyond the century mark, with projections indicating that by 2050, there could be half a million centenarians in the U.S. alone.
While some individuals live longer than the average life expectancy, the average for the U.S. is about 79 years, reflecting disparities in health outcomes around the world.