Often, the prevalence ratios of disability (for example) by single years of age show considerable fluctuations due to sampling variations. Thus, it is preferred to use average prevalence ratios for a five or ten years age interval for Sullivan method. It implies to estimate the total years of life lived in such age intervals. There are two possibilities:

- The use of a classical abridged life table. An abridged life table contains columns similar to those of the complete life table; the only difference is the length of the intervals. The length of a typical interval in the abridged life table is , which is greater than one year. Formulae from 9 to 13 can be extended in that case.
- The use of an abridged life table with values of derived
from the life table (i.e. ) and values of calculated
by summing values of for single years of age
*x*from the unabridged life table. In the example above (see 1.3), were calculated with the following formulae:

Because the second method is generally more accurate, it is highly recommended to use it if possible.

Fri Apr 25 22:40:35 DFT 1997