Mr. Nickles! Please read more carefully. I specifically said "the NUMBER of Americans," not the percentage. I'm sure you realize that your attempt at objectivity miserably fails when one considers that the percentage of elderly and retirees has mushroomed since the 70s.
The charts of working Americans shows a rise from the 70s to now, in absolute terms. There have been dips, thanks to Reagan and Bush policies (reversed, with grand results, by Clinton and Obama).