We make automatic cost-of-living increases if the applicable index, either the CPI or the AWI, rises over a specified measuring period (see the rules on measuring periods in § 404.274). If the cost-of-living increase is to be based on an increase in the CPI, the increase is effective in December of the year in which the measuring period ends. If the increase is to be based on an increase in the AWI, the increase is effective in December of the year after the year in which the measuring period ends.