53 - You bring up a very interesting point, but you come to the wrong conclusion - "I think the problem is that someone supports you until you're about 20 or so, if you work 20 years and live until 40, then no one will have to support you after you die"
Very good - you are a break even, if you live to 40. But if you live to 60, then you can support an extra 20 year old. And if you live and work till 70, then you support an extra 1.5. And if you live to 80, and still retire at 70, (the new retirement age) you still support an extra 1 up to 20 year old.
Yes, I just meant those who plan to retire at 60 and live till 80 or 90. My grandfather didn't retire from full time work until he was 84 and then died at 86.