[2] In order to adjust for age, a standard population must be selected.
Some agencies which produce health statistics also publish standard populations for age adjustment.
Standard populations have been developed for specific countries[3] and regions.
[5] These agencies must balance between setting weights which may be used over a long period of time, which maximizes comparability of published statistics, and revising weights to be close to the current age distribution.
When comparing data from a specific country or region, using a standard population from that country or region means that the age-adjusted rates are similar to the true population rates.