Mortality rates: crude and specific
- Measure
They count how many people die in a population over a period. The crude rate looks at everyone; specific rates look at one age group, sex or cause.
What it is
The crude mortality rate divides all deaths in a period by the mid-period population. Specific rates restrict both numerator and denominator to the same group (age, sex), or restrict the numerator to one cause. Proportional mortality is not a rate: it is the share of all deaths that belongs to one cause.
Formula and reading
- Crude rate = (deaths from all causes in the period / mid-period population) × 10ⁿ.
- Age-specific rate = (deaths in the age group / population of that group) × 10ⁿ.
- Cause-specific rate = (deaths from the cause / total mid-period population) × 100,000.
- Proportional mortality = (deaths from the cause / all deaths) × 100, as a percentage.
- The mid-period population (for example, on 30 June) approximates the person-years lived during the year.
Worked example
- A made-up municipality has 80,000 people at mid-year (39,000 men and 41,000 women) and records 560 deaths in the year.
- Crude rate: 560 / 80,000 = 0.007; × 1,000 = 7.0 deaths per 1,000 population.
- By sex: 308 deaths in men / 39,000 = 7.9 per 1,000; 252 in women / 41,000 = 6.1 per 1,000 (rounded to one decimal).
- By age: 6,000 people are 65 or older and 312 of the deaths occur among them: 312 / 6,000 × 1,000 = 52 per 1,000.
- By cause: 168 deaths are cardiovascular: 168 / 80,000 × 100,000 = 210 per 100,000 population.
- Cardiovascular proportional mortality: 168 / 560 = 0.30, that is, 30% of all deaths.
- Reading: the risk of dying at 65 or older is more than seven times the overall rate, and three in ten deaths are cardiovascular.
What goes on top and what goes below in each measure
| Measure | Numerator | Denominator | Usual multiplier |
|---|---|---|---|
| Crude rate | All deaths | Total mid-period population | 1,000 or 100,000 |
| Age-specific | Deaths in that age group | Population of that age group | 1,000 or 100,000 |
| Sex-specific | Deaths in that sex | Population of that sex | 1,000 or 100,000 |
| Cause-specific | Deaths from that cause | Total mid-period population | 100,000 |
| Proportional mortality | Deaths from that cause | All deaths | 100 (percentage) |
Markers
- CDR
- Specific rate
- Proportional mortality
- × 100,000
How to read it
- Age-specific rates are the raw material of standardisation and of life tables.
- In Colombia, deaths come from the death certificates that doctors fill in; their quality sets the quality of cause-specific rates.
Common pitfalls
- Using total deaths as the denominator and calling it a rate: that is proportional mortality.
- Comparing crude rates of populations with different age structures without standardising.
- Forgetting the multiplier, or mixing ‘per 1,000’ with ‘per 100,000’ when comparing.
Test yourself
Think of the answer, then tap the question to see it.
What denominator does the cause-specific mortality rate use?
The total mid-period population; the numerator is only the deaths from that cause.
How does proportional mortality differ from a rate?
Its denominator is all deaths, not the population; it says what share of deaths belongs to a cause, not the risk of dying from it.
Why can a city with many older adults have a high crude rate without worse health?
Because mortality rises with age; the crude rate reflects the age structure. Comparisons use specific or standardised rates.
If a population of 20,000 has 50 deaths in a year, what is the crude rate per 1,000?
50 / 20,000 × 1,000 = 2.5 deaths per 1,000 population.
Connections
Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources.
Sources: Principles of Epidemiology | Lesson 3 - Section 3 (Centers for Disease Control and Prevention, 2012); Age adjustment (National Center for Health Statistics, Centers for Disease Control and Prevention, 2026).
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Representative model, for educational purposes only.