Definition
Mortality rate is the proportion of a defined population that dies within a specified period of time, most commonly expressed as deaths per thousand or per hundred thousand people per year.
Why it matters
Mortality rate is the basic measurement unit of mortality science — every other concept in the field, including life expectancy, survival curves, hazard rates, and actuarial pricing, is derived from mortality rates measured across populations and ages. Without a measurement unit, the longevity dimension of lifetime income cannot be quantified, compared, or priced.
How it works
A mortality rate has three structural specifications that determine its meaning: the population being measured (age range, sex, cohort, geography), the time period over which deaths are counted (typically a single calendar year), and the form of the denominator (the population alive at the start of the period, the midyear population, or person-years lived through the period). A crude mortality rate uses the full population as the denominator without age adjustment; an age-specific mortality rate uses only the population in the relevant age group, which is the form actually used in actuarial work. A period mortality rate reflects the mortality conditions of a specific calendar year; a cohort mortality rate follows a specific birth cohort across its lifetime and incorporates how mortality has actually evolved for that cohort. Concrete figures from US data: in 2023, the age-specific mortality rate for women aged 67 was approximately 9 deaths per 1,000 per year, and the rate for women aged 85 was approximately 55 per 1,000 per year.
In practice
For an individual, the mortality rates that matter most are not the population-wide crude rates that appear in news coverage, but the age-specific rates at the ages they expect to encounter. A professional working with a life insurance application, an annuity quote, or a retirement projection is using age-specific mortality rates as inputs, drawn from period tables, projected tables, or cohort tables depending on the application. The participant rarely needs to read mortality rates directly, but should be able to ask whether a projection assumes static mortality (period rates held fixed) or accounts for ongoing improvement (a projection-grade table). The answer materially affects the projected lifespan and therefore the analysis of any long-horizon arrangement.
In the Longevity Standard Framework
Mortality rate is supporting vocabulary in the Longevity Standard framework. The framework's actuarial engine uses Gompertz-form mortality rates with Society of Actuaries credibility scaling to construct the survival curves that drive cost-of-income comparisons; mortality rates are the substrate from which the frictionless pool benchmark, the solo drawdown baseline, and the commercial SPIA and DIA product benchmarks are all derived. The framework treats the population-level rate as an analytical input rather than a target — what matters in the cost-of-income calculation is the rate at each age along the individual's planning horizon, not a single summary statistic.
Related terms
- Life expectancy
- Survival curve
- Hazard rate
- Force of mortality
- Mortality table
- Period life table
- Cohort life table
- Mortality credits