5 years of life for the deceased in their year of death. This generally holds for all ages, except for the youngest age group, and probably for the oldest age group as well (above 80) [1-3]. Looking at infant mortality, the striking feature is indeed that most of the deaths among live births are concentrated in the very find more first days. This fact urges us to adopt some factor k notably inferior to 0.5 for the mean proportion of the calendar year lived by infants who die in their first year of life. Our aim is to assess this factor k by analyzing data for the Flemish Region in Belgium. Which kinds of k-factor(s) should be considered, however, depends on the sort of life table used.

Location of k-factors within the life table Usually, life expectancies are derived from so-called period life tables in which age-specific mortality risks Inhibitors,Modulators,Libraries based on observations that occurred within successive birth cohorts in a given period of time (typically a calendar year), are applied to one hypothetical birth cohort under the assumption that the risks do not change over time. Two models of period life tables can be distinguished, depending on the kind of age groups that are observed: a) one with the age at the start of the calendar year (or equivalently, the age ‘attained’ at the end of the calendar year), and b) one with the age at the last birthday Inhibitors,Modulators,Libraries [2,4]. This is also referred to as age expressed in completed years versus age in exact years, respectively. Inhibitors,Modulators,Libraries Figure Figure11 illustrates on a Lexis-diagram, with calendar year on the x-axis and age on the y-axis, the way in which the successive birth cohorts build up the hypothetical birth cohort in both models.

Figure 1 Lexis diagram. Lexis diagram for observations in the calendar year t and its projection on the hypothetical Inhibitors,Modulators,Libraries cohort, in a model (a) with age attained on January 1st and (b) with age at last birthday. To calculate life expectancy (at birth), it is necessary to ascertain correct values for the person-years lived in each of the discerned parallelograms of the hypothetical Inhibitors,Modulators,Libraries cohort in both models, and in the case of the model with age reached on January 1st, also in its base triangle a1. In doing so, it is noteworthy that in model (a) with age attained on January 1st, each parallelogram depicting one age group or birth cohort actually covers 2 ages, whereas in model (b) with age at last birthday, each age group covers 2 birth cohorts (suitably projected on 2 calendar years in the hypothetical birth cohort).

In model (a), we assume that the newborns of year t who survive until the end of the year, will on average have lived 0.5 years insofar as births are uniformly spread over the entire calendar year. This can be AV-951 deduced from the length of the midline connecting the midpoints of the rectangular sides in triangle a1.