The increase for a coming year is based on inflation between the third quarter of the prior year and the third quarter of the current year, as measured by the Consumer Price Index for Urban Wage Earners and Clerical Workers, or CPI-W. In the third quarter of 2008 energy prices and the CPI-W spiked, giving beneficiaries a hefty 5.8 % COLA for 2009.
FORBES: Social Security: No COLA, No Payroll Tax Increase In 2011