the same index can be applied to occupational distributions table a summarises how these components are obtained based on and population census data on the labour force lf similarly retirees are those in the labour force who were aged and above in minus those aged and above in temporary withdrawals and reentries prior to definitive retirement are implicitly netted out the change in the size of the primeage group equals the labour force aged in minus the labour force aged in finally the number of new immigrants is calculated as immigrants with duration of residence of less than five years and such immigrants are excluded from the other components to avoid double counting as can be verified from the table these four components add up to the labour force in both and