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Comments on the use of life tables

Here, we are going to describe columns of the complete life table: (see [4] for more details but we call W the last interval tex2html_wrap_inline1224 ):

  1. Age interval [x,x+1[. Each interval in this column is defined by the two exact ages stated except for the final age interval.
  2. Proportion of those alive at age x dying in the interval [x,x+1[, tex2html_wrap_inline1232 . They are derived from the corresponding age-specific deaths rates of the current population, using formulae:


    where tex2html_wrap_inline1234 with tex2html_wrap_inline1236 is the age-specific death rates, tex2html_wrap_inline1238 the number of deaths at age x registered and tex2html_wrap_inline1242 is the midyear (calendar year) population during the calendar year. For a', see after.

  3. Number of living persons at age x, tex2html_wrap_inline1248 .


    For tex2html_wrap_inline1250 , see after.

  4. Number dying in interval [x,x+1[, tex2html_wrap_inline1254 .

    tex2html_wrap_inline1248 , tex2html_wrap_inline1254 and tex2html_wrap_inline1260 are related by:



  5. Fraction of last year of life for age x, tex2html_wrap_inline1264 . Each of the tex2html_wrap_inline1254 people who have died during the interval [x,x+1[ has lived x complete years plus a fraction tex2html_wrap_inline1264 of the last year. tex2html_wrap_inline1264 is often considered to be 0.5 on average, except for the first fourth age groups.
  6. Number of years lived by the total cohort in interval [x,x+1[, tex2html_wrap_inline1186 . It follows that:



  1. The previous approximation ( tex2html_wrap_inline1278 ) is less valid for the first years of life (from one year of age to four). However, the result remain close enough to the more realistic one to permit also this approximation for these age groups.
  2. Although the same method is used, reliability may differ between countries, for example, because of differences in methods of measuring the tex2html_wrap_inline1280 .

Eric Hauet
Fri Apr 25 22:40:35 DFT 1997