On the other hand, trials at CIMMYT's principal wheat-breeding station at Obregon in Mexico indicate a slowdown in potential yield growth to only 0.4% a year.

High Yield bonds usually pay a semi-annual coupon followed by a lump sum of the principal at maturity.

But when the yield falls short, funds pay investors from their principal. Asset managers suspect that plenty of investors do not fully understand this, and will be furious when they find out.