If the top federal earner is in the Civil Service Retirement System (CSRS), he/she does not pay FICA element for Social Security.
Of course, he/she does not get Social Security unless he/she has worked elsewhere & then his/her benefits are calculated using a formula that reduces the benefit up to about 50%.
For 2009, CSRS employees will receive a 5.8% increase in their retirement pay. Federal Employee Retirement System (FERS) retired employees will get a 4.8% increase - they payed into Social Security, so they get that, too. I believe the Social Security increase for 2009 is 6.9%.