Biggest Ponzi Scheme Ever?

So, I read in the news today about “Bernard Madoff, who pleaded guilty today to masterminding the largest Ponzi scheme in history…”

I’m confused. Isn’t the biggest Ponzi scheme in history the US Social Security System?

(Ponzi Scheme, from Wikipedia: “pays returns to investors from their own money or money paid by subsequent investors rather than from any actual profit earned. … other English-speaking countries do not distinguish colloquially between this scheme and pyramid schemes…. The perpetuation of the high returns that a Ponzi scheme advertises and pays requires an ever-increasing flow of money from investors in order to keep the scheme going. The system is destined to collapse because the earnings, if any, are less than the payments.”)