Because the life expectancy differs between females and males, between 20- and 80-year old persons, and because it was shorter in 1800 than it will be in 2002, the analyses of mortality needs standardization. The standardized mortality ratio (SMR) is the ratio of observed and expected number of deaths. The expected death is the multiplication of the years lived by persons of the pedigree in each calendar period for each age and sex category by the age and sex specific mortality rates of the Dutch population for each calendar period.