"...COLAs for retirees are governed by a formula set in law. They are determined in reference to the Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W), as calculated by the Bureau of Labor Statistics. As of the end of June, the CPI-W had increased 1.6 percent in the previous 12 months.
The 2013 COLA for retirees will be determined based on the results posted at the end of September 2012. That means price increases and decreases during July, August and September will affect the COLA that retirees receive in their Civil Service Retirement System and Federal Employees Retirement System benefit checks payable on Jan. 1, 2013..."