It follows from the definition that if we consider the simplest case
of two states of health which we will call Disability Free (DF) and
Disabled (D) and if is the proportion of disabled in
the age group *i*, we can calculate two sorts of Sullivan Indices:

- Indices of healthy state of the population for different age groups
(here we denote , which means
*Disability Free Life Expectancy at age*): - Indices of unhealthy state of the population for different age
groups (here we denote , which means
*Disabled Life Expectancy at age*:

Thus, we can make three remarks:

- The classical indicator summarizing the mortality experience of
the population, the expectation of life at age (denoted ),
has been decomposed into a disability-free and disabled component.
Indeed,
- Like life expectancies, the indicators and are independent of the age structure of the population of persons aged and older.
- Since health expectancy includes both mortality and morbidity
into a single indicator, it is sometimes preferred to the total life
expectancy index for populations with low mortality but high
morbidity rates.

Fri Apr 25 22:40:35 DFT 1997