22 January 2008: The Fed slashes rates in an emergency

After global stocks plunged while US markets were closed for the Martin Luther King holiday, the Federal Reserve cut its key rate by three-quarters of a point before the opening bell, an unscheduled move not seen in decades. Days later it emerged that Societe Generale had been unwinding billions in positions from a rogue trader. The cut steadied markets briefly, but the financial crisis was only getting started.

The lesson: An emergency rate cut tells you the central bank is worried, which is not exactly reassuring.