Expectations
of life can be calculated in two ways: ‘
period
life expectancy’ or
‘cohort
life expectancy’.
Period
life expectancies are worked out using the age-specific
mortality rates for a given period (either a single year,
or a run of years), with no allowance for any later actual
or projected changes in mortality.
Cohort life
expectancies are worked out using age-specific mortality
rates which allow for known or projected changes in mortality
in later years.
For example, period life expectancy at age 65 in 2000 would
be worked out using the mortality rate for age 65 in 2000,
for age 66 in 2000, for age 67 in 2000, and so on. Cohort
life expectancy at age 65 in 2000 would be worked out using
the mortality rate for age 65 in 2000, for age 66 in 2001,
for age 67 in 2002, and so on.
Period life expectancies are a useful measure of mortality
rates actually experienced over a given period and, for
past years, provide an objective means of comparison of
the trends in mortality over time, between areas of a country
and with other countries. Official life tables in the UK
and in other countries which relate to past years are generally
period life tables for these reasons. Cohort life expectancies,
even for past years, may require projected mortality rates
for their calculation.
Period life expectancies are sometimes mistakenly interpreted
by users as allowing for subsequent mortality changes. Period
life expectancy answers the question ‘For a group
of people aged x in a given year, how long would we expect
them to live, on average, if they experienced the age-specific
mortality rates above age x of the period in question over
the course of their remaining lives?’
The cohort life expectancy answers the question ‘For
a group of people aged x in a given year, how long would
we expect them to live, on average, if they experienced
the actual or projected future age-specific mortality rates
not from the given year but from the series of future years
in which they will actually reach each succeeding age if
they survive?’ If mortality rates at age x and above
are projected to decrease in future years, the cohort life
expectancy at age x will be greater than the period life
expectancy at age x.
Period and cohort life expectancies at birth and five-yearly
age intervals for the years 1981 to 2053 for the United
Kingdom and its constituent countries calculated using historic
mortality rates and projected mortality rates from the interim
2003-based national population projections can be accessed
from the links in the table below.
Period and
cohort life expectancies for males and females,
1981 to 2053
|
| United
Kingdom |
|
|
| Great Britain |
Period |
Cohort |
| England and Wales |
Period |
Cohort |
| England |
Period |
Cohort |
| Wales |
Period |
Cohort |
| Scotland |
Period |
Cohort |
| Northern Ireland |
Period |
Cohort |
| United Kingdom,
High life expectancy variant |
|
|
| United Kingdom,
Low life expectancy variant |
|
|
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Graphs showing period and cohort life expectancies at birth
and at age 65 can be accessed by clicking on the links in
the table below.
Period and
cohort life expectancies for males and females at
birth (EOLB) and at age 65 (E65), 1981 to 2053
|
| United
Kingdom |
|
|
| Great Britain |
EOLB |
E65 |
| England and Wales |
EOLB |
E65 |
| England |
EOLB |
E65 |
| Wales |
EOLB |
E65 |
| Scotland |
EOLB |
E65 |
| Northern Ireland |
EOLB |
E65 |
| United Kingdom,
High life expectancy variant |
|
|
| United Kingdom,
Low life expectancy variant |
|
|
