Risk Modelling and Survival Analysis · Mortality projection

Mortality Trends and Drivers of Improvement Explained

Updated 11 October 2026 · Fact-checked

Mortality improvement is the fall in death rates at given ages over time. Main drivers are medical advances, better public health, nutrition, lifestyle change and rising income and education. Future rates are uncertain because these drivers can speed up, slow down or reverse. In exams, name the driver, explain its effect, and link it to longevity risk.

Understand Mortality Trends and Drivers of Improvement

Mortality is the rate at which people die at each age. A mortality trend is how those rates change over calendar time. Over the last century, rates at most ages have fallen in most countries. This fall is called mortality improvement. It means a person aged 65 today usually has a lower chance of dying in the next year than a person aged 65 did decades ago.

Improvement has not been steady. In the early twentieth century, most gains came from falling deaths at young ages, mainly from infectious disease, poor sanitation and infant deaths. Later gains came more from falling deaths at older ages, mainly from heart disease and stroke. So the age pattern of improvement shifts over time. Different causes of death also improve at different speeds, so the overall trend is a mix of many trends.

The main drivers of improvement fall into groups:

Medical advances: vaccines, antibiotics, better surgery, drugs for blood pressure and cholesterol, earlier screening and better treatment of cancer.
Public health and environment: clean water, sanitation, better housing, cleaner air and fewer infectious outbreaks.
Lifestyle and behaviour: lower smoking in many groups, better nutrition, more awareness of exercise and health.
Socio-economic change: higher income, more education, better access to healthcare, and better working conditions.

Some forces push the other way. Obesity, diabetes, air pollution, antibiotic resistance, new pandemics and inequality in access to care can slow improvement or raise mortality for some groups. In India, many gains came from falling infant and child deaths and better control of infectious disease. Non-communicable disease is now a growing concern, and gaps between rural and urban areas and between income groups remain.

Future mortality is uncertain. Nobody knows if medical breakthroughs will come, if lifestyle risks will grow, or if past rates of improvement will continue. Improvement can also differ by cohort, which means people born in the same period. Some generations have shown faster improvement than others. This uncertainty gives rise to longevity risk: the risk that people live longer than assumed, so annuity and pension payments last longer and cost more than expected. Insurers and pension schemes therefore cannot use a fixed current table for long-term liabilities. They need projections and a view of how wrong those projections could be.

Key rules to remember

Mortality improvement rate: Improvement rate = 1 − q(x, t+1) ÷ q(x, t); Proportional fall in the rate at age x from year t to t+1. A positive value means improvement. Defined for q(x, t) > 0.
Reduction factor over n years with constant annual improvement: q(x, t+n) = q(x, t) × (1 − r)ⁿ; Applies only if the improvement rate r is the same each year. Real improvement is rarely constant, so state this as an assumption.
Types of uncertainty in projections: Model risk, parameter risk, stochastic (random) risk; Remember these three. Model risk is the wrong structure, parameter risk is poorly estimated inputs, and stochastic risk is random variation in actual deaths.
Groups of drivers: Medical, public health, lifestyle, socio-economic; Use this list to structure descriptive answers.

How to solve Mortality Trends and Drivers of Improvement questions

Use this method for descriptive questions and for short calculation questions on trends and drivers.

1Read the command word. 'Describe' needs facts, 'explain' needs reasons, and 'discuss' needs both sides.
2Identify the population: age range, sex, country, and whether it is a pension scheme, annuity book or life insurer.
3List the relevant drivers in groups: medical, public health, lifestyle, socio-economic. Add factors that reverse improvement.
4For each driver, say how it affects mortality, at which ages and for which causes of death.
5Link to the actuarial consequence: longevity risk for annuities and pensions, or mortality risk for protection business, and how pricing and reserving are affected.
6For calculations, apply the improvement formula year by year or with the power form. State the assumption of constant improvement.
7State the uncertainty: the future may differ from the past, so projections should use scenarios or stochastic models.
8Check that your answer has enough distinct points for the marks available.

Quickest way: Four-group checklist for driver questions

When to use it: Use it when a question asks for causes or factors of mortality change and time is short.

Write four labels: Medical, Public health, Lifestyle, Socio-economic.
Put one or two specific points under each label.
Add one point on factors that could slow or reverse improvement.
Finish with one line on why this creates uncertainty and longevity risk.
For numbers, use q × (1 − r)ⁿ and check the result is smaller than the starting rate.

Common mistakes in Mortality Trends and Drivers of Improvement

Listing drivers with no explanation of how they affect mortality.
Students memorise a list and stop at the heading.
Fix: Write a short reason for each point, such as 'vaccination reduces deaths from infectious disease at young ages'.
Assuming improvement is the same at all ages and causes of death.
A single average improvement figure hides the detail.
Fix: Say that improvement varies by age, sex, cause of death, period and cohort.
Assuming past improvement will continue unchanged.
Extrapolating a trend feels natural.
Fix: State that drivers can fade or reverse, so the future is uncertain and scenarios are needed.
Confusing longevity risk with mortality risk.
Both relate to death rates.
Fix: Longevity risk is people living longer than expected, which hurts annuity and pension providers. Mortality risk is people dying sooner than expected, which hurts protection writers.
Applying an improvement rate as an additive change instead of a proportional change.
Students subtract r from q.
Fix: Multiply: q × (1 − r) for each year of improvement.
Forgetting factors that worsen mortality.
The topic is called improvement, so only positives come to mind.
Fix: Include obesity, diabetes, pollution, pandemics and inequality for balanced discussion answers.

Worked examples

Example 1

The mortality rate at age 70 for a population is q = 0.020 in the current year. Assume mortality at age 70 improves by 2% a year, proportionally and at a constant rate. Calculate the projected rate at age 70 in 10 years' time.

Show the solution

Use q(x, t+n) = q(x, t) × (1 − r)ⁿ with r = 0.02 and n = 10.
Compute 0.98¹⁰. 0.98² = 0.9604. 0.98⁴ = 0.9604² = 0.92237. 0.98⁸ = 0.92237² = 0.85076. 0.98¹⁰ = 0.85076 × 0.9604 = 0.81707.
Multiply: 0.020 × 0.81707 = 0.016341.

Answer: The projected rate is about 0.0163. This is a fall of about 18.3% from 0.020.

Example 2

A pension scheme in India prices its pensions using a current mortality table with no allowance for future improvement. (a) Explain why this is risky. (b) Describe four drivers that may lead to continuing improvement and two that may reduce it.

Show the solution

Part (a): the scheme pays pensions for life. If members live longer than the table assumes, payments continue for longer and cost more. This is longevity risk.
The effect builds over many years, so a small unallowed improvement each year can cause a large shortfall in liabilities.
Part (b), improvement: medical advances such as better treatment of heart disease and cancer reduce deaths at older ages.
Public health measures such as clean water, sanitation and vaccination cut deaths from infectious disease.
Lifestyle change such as lower smoking and better nutrition in some groups reduces disease.
Socio-economic change such as higher income, education and access to healthcare improves survival.
Part (b), slowing factors: rising obesity and diabetes raise deaths from related disease. New pandemics, antibiotic resistance or pollution may raise mortality.
Conclude: the future is uncertain, so the scheme should allow for improvement using projections and test the effect of different scenarios.

Answer: No allowance for improvement understates liabilities and exposes the scheme to longevity risk. Improvement drivers include medical, public health, lifestyle and socio-economic change. Obesity, diabetes, pandemics and pollution may slow or reverse it, so the scheme should use projections and scenarios.

Exam tips

Structure descriptive answers by driver group and add reasons, not only labels.
Always link drivers to a business consequence such as longevity risk for annuities and pensions.
In calculations, state that improvement is proportional and assumed constant, then show the power step.
Mention that improvement differs by age, sex, cause of death and cohort. Examiners reward this detail.
Include at least one factor that may slow improvement to show balance in 'discuss' questions.

Practice questions from Mortality projection

Mortality Trends and Drivers of Improvement: frequently asked questions

What is mortality improvement?

It is the fall in death rates at a given age over calendar time. It is usually measured as the proportional reduction in the mortality rate from one year to the next.

Why does future mortality remain uncertain?

Drivers such as medical progress, lifestyle and income can change speed or direction. New diseases and treatments are hard to predict. Even the best model can have the wrong structure or poorly estimated parameters.

What is longevity risk and who bears it?

Longevity risk is the risk that people live longer than assumed. Annuity providers and pension schemes bear it because they pay benefits for life. Longer lives mean higher cost than expected.

Does mortality improve equally in all age groups?

No. Early gains were mainly at young ages from controlling infectious disease. Later gains were larger at older ages from better treatment of circulatory disease. Rates also differ by sex, cause of death and cohort.