Stock market indices are tough for the average fund manager to beat. Over time, no more than a fifth of the world's managers have any chance of outperforming them.

The efficient-market hypothesis has taken a hammering of late. But it remains true that, most of the time, share prices - and indices - are the best reflection of current circumstances. Even when the rule breaks down during booms and slumps, indices can do better than the average active fund manager.