Say you buy $100 worth of bitcoin thinking the price will go up 20%. If it does, and you cash out, you’ll end up with a profit of $20. But what if you could buy $1,000 worth of bitcoin with only $100 ...

South Korea’s main stock index fell 20% over two trading sessions, as leveraged bets by retail investors spiraled into margin calls and forced selling. The sudden slide, centered in Seoul, rattled ...