Final answer:
Life expectancy is defined as the average number of years individuals in a specific birth year are expected to live, with varying figures based on location and lifestyle factors. Many individuals exceed these averages, and various factors such as healthcare and nutrition influence life expectancy rates.
Step-by-step explanation:
Life expectancy is the average number of years that a group of people born in the same year could expect to live. Although it is just an average, many individuals outlive the predicted number. By 2050, it is estimated that half a million Americans will be at least 100 years old. Factors such as nutrition, healthcare, clean water, sanitation, and exercise can influence life expectancy rates, which vary across different regions. For example, in the United States, the life expectancy is approximately 79 years old, whereas Monaco has the highest at 89.57 years and Chad has the lowest at 49.44 years. Life tables can provide additional insights into the life history of a population, indicating the probability of mortality at various ages.