Arabica coffee has been the biggest climber this year but the biggest loser in May as the Brazilian coffee harvest began and production levels were estimated to be higher than originally feared. The key crops of corn and especially wheat ran into heavy selling during May as planting progressed at a strong pace and favourable weather across the northern hemisphere raised the spectre of a bumper crop.

Gold continued its fall from grace, losing more than 3 percent in May.  Just as equity markets continue to put in a strong performance, it's reduced the need for alternative investments in portfolios.