It is possible, however, that the industry faces a sharply rising average-cost curve, so that the costs of the efficient firms are lower than the market price.

Recycled gold coming onto the market rose 35% to 496 metric tons as the rising price of the metal "encouraged consumers to sell their existing holdings," the group said.

A falling share price suggests that the market thinks it increasingly likely that profits have peaked, but analysts forecast that they will keep rising.