How Do You Calculate Total Fertility Rate and Life Expectancy?

• French B
• Geography
• German A
• German A Lit
• German ab initio
• German B
• Global Politics
• History
• History (First Exam 2028)
• Mathematics Analysis and Approaches (AA)
• Mathematics Applications & Interpretation (AI)

• Philosophy
• Physics
• Psychology
• Psychology (First Exam 2027)
• Spanish A
• Spanish A Lit
• Spanish ab initio
• Spanish B
• Sports, exercise and health science (SEHS)
• Theory of Knowledge (TOK)
• World Religions

• MYP English Lang & Lit
• MYP Extended Mathematics
• MYP History

• MYP Individuals & Societies
• MYP Integrated Sciences
• MYP Physics

• MYP Standard Mathematics

For example, if the ASFR values across all seven age groups sum to $400$:

The estimated TFR is therefore $2.0$ children per woman. The factor $5$ represents the width of each age interval.

Life Expectancy

Life expectancy is not normally calculated by averaging the ages at which people died. Demographers construct a life table using age-specific mortality rates. If $T_x$ is the total person-years remaining above age $x$, and $l_x$ is the number surviving to that age:

For a hypothetical population with $100{,}000$ survivors at birth and $8{,}100{,}000$ total person-years remaining:

A common misconception is that these measures predict one woman's family size or one person's lifespan. They are population-level estimates based on current fertility and mortality patterns.

Exam Technique

For a calculation, show the formula, substitution, answer and units. In data-response questions, also interpret the result and link changes in TFR or life expectancy to population growth, age structure and the demographic transition model. Any required equation will be provided in the ESS question.