Timing the market is dangerous. Most people should not attempt it. But early this week, several analysts warned that an equity market correction or sell-off was imminent. This week, right on cue, western equity markets are selling off.

In the past two trading sessions, the FTSE-Eurofirst 100 was off 2.3 per cent. The S&P was off 1.4 per cent. Is this a pause after a rally, or the start of a correction? And how can analysts tell the difference?