Background
There are two types of life tables:
- Period or static life tables show the current probability of death (for people of different ages, in the current year)
- Cohort life tables show the probability of death of people from a given cohort (especially birth year) over the course of their lifetime.
Static life tables sample individuals assuming a stationary population with overlapping generations. "Static Life tables" and ""cohort life tables" will be identical if population is in equilibrium and environment does not change. "Life table" primarily refers to period life tables, as cohort life tables can only be constructed using data up to the current point, and distant projections for future mortality.
Life tables can be constructed using projections of future mortality rates, but more often they are a snapshot of age-specific mortality rates in the recent past, and do not necessarily purport to be projections. For these reasons, the older ages represented in a life table may have a greater chance of not being representative of what lives at these ages may experience in future, as it is predicated on current advances in medicine, public health, and safety standards that did not exist in the early years of this cohort.
Life tables are usually constructed separately for men and for women because of their substantially different mortality rates. Other characteristics can also be used to distinguish different risks, such as smoking status, occupation, and socioeconomic class.
Life tables can be extended to include other information in addition to mortality, for instance health information to calculate health expectancy. Health expectancies such as disability-adjusted life year and Healthy Life Years are the remaining number of years a person can expect to live in a specific health state, such as free of disability. Two types of life tables are used to divide the life expectancy into life spent in various states:
- Multi-state life tables (also known as increment-decrement life tables) are based on transition rates in and out of the different states and to death
- Prevalence-based life tables (also known as the Sullivan method) are based on external information on the proportion in each state. Life tables can also be extended to show life expectancies in different labor force states or marital status states.
Read more about this topic: Life Table
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