[alister]

Here's another illustration of how our intuition about compound interest can be really wrong:

Futurama scene where Fry has been transported to the year 3000 and he still has his ATM card: The bank teller checks Fry's bank balance. She says, "You had 93 cents in your account in 2000. With an average interest rate of 2.25% compounded for 1000 years . . . that brings your balance to $4.3 billion dollars."

The math is correct. Plug those numbers into the compound interest formula, Pn = P0 (1 + r/100)^n, and you really do get $4.3 billion.

Your gut feeling is that even with 93 cents, you could retire rich. Not a billionaire, but comfy. It ain't so. In 50 years, you'd have $2.83. And even that $2 gain would be wiped out by a single monthly banking fee :-).

In 400 years, $6820. My intuition told me that I should be in the millions by then. Wasn't even close. Didn't even account for taxes and inflation.

[misja111]

Another thing that many people forget is that while compound interest gives you more money, at the same time inflation makes your money worth less. So what you should really be looking at is the difference between the inflation and the interest rate: the so called 'real interest rate'. Currently in the US, that rate is negative ..

[JBReefer]

I feel like I can't get a handle on the inflation numbers I see. I pay - and the math checks out - roughly the same amount for gas, produce, and essentials. My smartphone is 1/3 the cost it was 10 years ago.

And then housing and health insurance is like 2.5 times higher. It all totals to be the official rate, but man does it feel uneven.