The difference is as wide as the Atlantic Ocean?

Though PolitiFact has determined that Social Security financing is definitely not a "Ponzi scheme," apparently the pay-as-you go retirement programs in southern Europe are Ponzi schemes:

(E)xperts warn of a looming demographic disaster in Southern Europe, which has among the lowest birth rates in the Western world. With pensioners living longer and young people entering the work force later — and paying less in taxes because their salaries are so low — it is only a matter of time before state coffers run dry.

“What we have is a Ponzi scheme,” said Laurence J. Kotlikoff, an economist at Boston University and an expert in fiscal policy.
(New York Times)

I don't get it.  Gov. Rick Perry says that Social Security's pay-as-you-go system is a Ponzi scheme and receives a "False" rating from PolitiFact.  Then "expert in fiscal policy" Laurence J. Kotlikoff says the same thing of a parallel system in Europe and the New York Times treats him as though he's some sort of expert?

Bring on PolitiFact Massachusetts!