As the traders watched the price charts, looking for waves that could be profitably surfed, they recognized recurring patterns. Market bottoms tended to be rounded, because a bumper harvest not only drives the price down but causes excess produce to be held in storage; this inventory overhang keeps prices low for an extended period. By contrast, market tops tend to be spike shaped: If there is a sudden shortage in a crop, consumption has to fall sharply and prices shoot up; but if the next harvest is good, the shortage goes away and prices quickly shoot down again.
