The Numbers aren't exactly true for the private side either! Stock Options, 401K, IRA contributions, Commissions, and bonus's are just a few that come to mind that are difficult at best to track and compare to the public sector. And are at least somewhat related to the economy.
Would offer that Job Security, although good in the federal sector isn't exactly a given. I have been through 3 Reduction's in Force/Outsourcing in this past 10 years. And some of my co-workers have been through a fourth one.