The COLA adjustment in January for federal retirement benefits will mean about a $50 per month increase in the average annuity paid under CSRS and about $20 a month to the average FERS annuity.

The inflation adjustment of 1.7 percent is the same for both systems; the formula pays lower amounts to FERS retirees if the inflation measure is higher than 2 percent. Earlier this year, for example, CSRS retirees received a 3.6 percent increase while FERS retirees received a 2.6 percent increase.

According to figures current through last October 1 there were 1,502,293 CSRS retirees and 391,455 FERS retirees, meaning about an 80-20 percent split.

In dollar terms—which would be a bit higher now, due to the January 2012 increases—under CSRS the average monthly annuity was $3,002 and the median (where half are above, half are below) was $2,620, while under FERS the figures were $1,097 and $823, respectively.

Survivor beneficiaries under CSRS outnumber those under FERS by an even wider margin, 545,701 to 40,060. The average and median survivor benefits under CSRS are $1,384 and $1,230, respectively, while the comparable figures for FERS survivor beneficiaries were $461 and $358.