How much do you need in your CPF and why does the figure in GIC look off?

By 2013, the minimum sum in your CPF is supposed to be $120,000.

How much are you supposed to have in your CPF so that it can automatically become $120,000 when you reach age 55, assuming the minimum sum is $120,000?

The table below gives your answer, assuming that the interest rate for CPF, which is 2.5% currently, doesn't change.

Suppose you're 31 this year^th, like... ? The amount you need to have in your CPF on your 31^st birthday needs to be $66345.04 just so that it can grow at an annual compounded rate of 2.5% to eventually reach $120,000 in your 55^th year.

According to statistics provided, Singaporeans can expect to have a life expectancy of 77 years old. If that's the case, assuming you have no other income, and that you can withdraw $120,000 equally, you're only entitled to $120,000 for 22 years (after 55 years old).

That's roughly $5454 per year after age 55, and every month, you're only getting $454.50. Can anyone really expect to survive on $454.50 every month?

Having read Business Times yesterday, MM Lee noted that the Government started GIC with S$6.4 billion in the year 1981, and that it averaged 9.5% in compounded growth annually over the past 25 years, and it now manages well over S$100 billion.

If that's the case, by this year, it would only have $61.88 billion. I'm wondering where the S$38+ billion came from.