Terminology

Studies of longevity, or long life, bring together many different disciplines.

A common language is terribly important to get the most from everyone’s contributions. Here we endeavour to explain in simple language some of the most commonly used terms from actuarial science, demography, medicine, pensions, and statistics. We hope that this is a useful reference point for those involved in different parts of the study of longevity.

No doubt there are other technical terms that you would like to be explained (or aspects of our definitions and explanations that may not be accepted by everyone). If so, please contact us and we will do our best to research a simple description.

 
Age rating
A crude way of tailoring a mortality table to fit the characteristics of a particular population.

Ageing
The process of deterioration of the physical condition of a living organism that ultimately leads to death.

Annuity
A financial instrument offered by an insurance company that resembles a pension

Baby boomers
A Baby Boomer is a person born between 1945 and 1965.

Base table
A set of age-specific rates of assumed mortality.

Biological age
Biological age differs from chronological age in that it takes account of the effect of genetic and environmental factors on an individual’s lifespan.

Biological limit on life
An ageing theory which postulates that humans (along with other species) have a natural limit to their lifespans that cannot be exceeded.

Birth cohort
A birth cohort is a group of people from a given population which is defined by the time of their birth.

Causes of death
In many countries, deaths are certified by doctors and certification data is collected.

Chronological age
Chronological age is age measured as time elapsed since the date of birth.

CMI – Continuous Mortality Investigation
A research project organised by the UK actuarial profession that collates mortality and morbidity data from UK insurers (and, latterly, from UK pension schemes) and produces mortality tables.

Cohort life expectancy
See expectation of life

Compression of mortality
Over time, the spread of ages over which individuals die (on average) has narrowed.

Covariate
A covariate is a potential differentiating factor that might explain some of the variation in mortality rates.

Death rate
See mortality

Demography
The study of populations.

Expectation of life
The length of time (generally measured in years) that an individual can expect to live.

Exposed-to-risk
Tthe number of individuals within a specified population who are ‘at risk’ of a specified event occurring to them or in relation to them.

Generation X
Those born in the 1960s and 1970s

Generation Y
Those born in the 1980s and 1990s.

Geo-demographics
The description of people according to where they live.

Geriatric
Geriatric medicine refers to the clinical, preventive and social aspects of illness in older people.

Gerontology
The study of ageing in humans.

'Golden Cohort' effect
A number of UK mortality studies have shown that the birth cohort of pensioners born around 1926 is, on average, living longer than those born earlier or later.

Graduation
The mathematical process of ironing out bumps in observed mortality rates at individual ages to produce smoothed mortality or survival curves.

Healthy life expectancy
An individual’s healthy life expectancy is the expected number of years of life in good, or fairly good, health.

Heterogeneous
A term commonly used in statistics, meaning ’containing diverse and different items’, or ‘displaying different characteristics’.

Homogeneous
Homogeneous means ’containing identical items’, or ‘displaying identical characteristics.’

Lee-Carter
The Lee-Carter model is a mathematical model for projecting historic trends in mortality improvements into the future.

Library of projections
In 2007 the CMI, on behalf of the UK Actuarial Profession, published a ‘library’ of mortality projections.

Life expectancy
See expectation of life.

Longevity
Longevity is often used to refer to long (or longer than expected) life.

Longevity swaps
A new and developing class of special financial instruments enabling two parties to exchange payments depending upon the mortality rates of a particular population.

Minimum improvements
Many projections for future improvements (i.e. reductions) in mortality rates (or increases in longevity) assume that these reductions will tend rather rapidly to zero.

Morbidity
Morbidity refers to the state of being sick or disabled, and to the incidence or prevalence of sickness or disability.

Mortality
Mortality is the susceptibility to death (‘mortal’).

Mortality improvements
Actuaries often refer to reductions in mortality rates as ‘mortality improvements’.

Mortality rate
See mortality and mortality table.

Mortality swaps
See longevity swaps.

Mortality table
A set of mortality rates by age – usually spanning ages 0 to 120.

Multi-variate statistics
A branch of mathematical statistics that helps to identify the strength of relationships and interdependencies in bodies of data that include many covariates.

ONS longitudinal study
The Office for National Statistics (ONS) longitudinal study started in 1971 as a means of understanding trends within the England & Wales population.

Period life expectancy
See Expectation of life.

Population pyramid
A popular type of chart used to depict the age and gender structure of a population.

Premature death
Death resulting from something other than old age.

P-spline
P-splines are a mathematical tool which is increasingly being used to analyse and extrapolate trends in historic mortality.

Scaling factor
A crude way of tailoring a base table to allow for the characteristics of a particular population, by multiplying the mortality rates by a scaling factor.

Select table
A particular form of mortality table that is used for sub-populations that have been selected in some way.

Senescence
The scientific name for ageing and relates to the biological processes which take place in individuals at older ages.

Short, medium and long cohort
Three different cohort projections have been produced by the CMI, each projecting the future of the ‘golden cohort’ differently.

Socio-economic group
The Office for National Statistics (ONS) defines socio-economic groups as groups ‘derived from occupation, employment status and size of establishment’.

Survival curve
A statistical graph of the survival experience or expectation of a population, showing the proportion surviving (or expected to survive) by age, or over time.

Tontine
A tontine is an early form of investment vehicle that combines features of a group annuity, group life assurance and lottery.

Vita
Latin for life.