Consequences

 

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:

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

    

2. 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.