Josh Barro and E.J. McMahon point out in this NY Post article that state and local pension benefits are generally twice as large as private sector pension benefits.
The productive loss to the economy caused by these high benefits is best exemplified by the whiny response from government union members: "I wouldn't have taken this job if I hadn't been promised that generous retirement."
By enticing people into the government and out of the private sector we lose any capacity their labor might have to meet the individual needs and desires of consumers, however modest that might be!
Of course, we also gain the interference with the private sector of too many regulators with too much power and too much time on their hands. After all, what else have they to do except perhaps while away the time till retirement, calculating and recalculating their benefits and ways to increase them.