22 December 1994: Mexico lets the peso float

Two days after a botched devaluation, Mexico abandoned its defense of the peso and let it float freely. The currency collapsed, losing about half its value within months, and investors fled Mexican stocks and bonds in what became known as the Tequila Crisis. The US organized a roughly $50 billion international rescue package. The crisis spread to other emerging markets and offered a preview of the Asian crisis three years later.

The lesson: Defending a currency with dwindling reserves usually ends with a sudden collapse.