It is well documented that investors often fare poorly in midyear. But August is a notable exception, and shares rise in three out of every four years.

In contrast, the odds of a price rise are close to 50:50 in surrounding months such as May, June and September.

Bull markets are especially good to August investors. Shares rise 85 per cent of the time during bull markets and the typical gain in August, the year's best bull market month, is near to 3.5 per cent - well over 200 points on today's FTSE 100.

In contrast August's bear market record has been awful throughout the century and is getting worse.

Since 1973, a bear market downturn was in progress as August began on eight occasions. Prices fell by at least 3 per cent in seven of those years and most drops were much larger - by almost 11 per cent in 1998, for instance.