The most important number in finance was fake.

A single daily rate called LIBOR helped set the interest on trillions of dollars of loans. It was based on banks self-reporting what they'd charge each other, and traders leaned on those reports to move the rate in their favour.

The rate was set on trust, not hard data, and the same banks that reported it also profited from where it landed. That's a conflict of interest with billions on the line, and it got abused.

If your mortgage, loan or credit card was priced off LIBOR, a rigged rate meant you could have paid more (or less) than you should have, decided by traders you'll never meet, for reasons that had nothing to do with you.