Compound interest: Einstein's 'eighth wonder of the world'

Whether or not Einstein actually said it, the quote attributed to him captures a profound truth: 'Compound interest is the eighth wonder of the world. He who understands it, earns it; he who doesn't, pays it.' A single £1,000 invested at 7% per year becomes £7,612 after 30 years with no additional contributions — purely through compounding. The same logic applies in reverse: a credit card balance left unpaid at 20% APR will double roughly every 3.6 years.

Source: Attributed to Albert Einstein; confirmed by mathematics