Compound interest is a joke for the 99%. My savings account gives me 0.65% interest I think? http://xkcd.com/947/ However when you start having millions on 10% interest you start talking real money, at least from the perspective of the person who will never have that kind of investment.
Compound interest is only a magical force on long term investing with decent interest (2% is fairly low for real investing). With a somewhat realistic 7% (usual growth of the S&P500) yield over 40 years, this is actually visible:
That was just one example though. And it's a quirk of the current moment-in-time that interest rates have been hovering around historical lows for some time now. But I stand by my overall point that lack of financial knowledge and wherewithal is a significant factor that inhibits upward mobility.
That's a little bit odd. Here in South Africa, you regularly get 'savings'-type accounts that yield 5+ percent interest, guaranteed by the bank. If it weren't for exchange controls, you'd probably have access to the sort of market (like South Africa) that would let you have that kind of interest rate.
Then again, we also have mortgage-loans that are at 10% interest.
There's no free lunch, that high interest rate has to be considered against the currency risk from the weak and unstable ZAR. In the last 5 years a 5% interest rate will have compounded to a 27% one. In the same time the ZAR has weakened against the USD by 125%.
You will not find a combination of a stable currency and high guaranteed interest rates anywhere.