"Social Security as we know it is a system in which each generation's payroll taxes are mainly used to support the previous generation's retirement. If contributions from younger workers go into personal accounts instead, the problem should be obvious: who will pay benefits to today's retirees and older workers? It's just arithmetic: 2-1=1. So privatization creates a financial hole that must be filled by slashing benefits, providing large financial transfers from the rest of the government or both"
Not only doesn't everyone know this, but I doubt that it is very well known at all. From the first SS has been presented as a savings system where workers put in their money and expect to take it out at retirement which is why we are constantly being told about the fictional "Trust fund". It has been from the first an enormous Ponzi scheme with bad actuarial assumptions from day one. Without significant cuts in benefits or increases in taxes the system will be insolvent by 2029. That's the simple arithmetic that Prof. Krugman doesn't seem to understand. While market returns most likely won't repeat their 90s performance in the near future, even if market returns are only 4% (which is a very low estimate) over the next decade it is still far better than the less than 1% returns workers get from their current SS contributions. I guess he missed those classes on the effects of small return differences when compounded while getting his PhD in economics. (I feel the urge for a longer rant but not enough time now, perhaps I will expand on it later. I'm sure the main KrugmanWatchers will pipe in too).