Basic foodstuffs don’t respond to market mechanisms in the way expected. Demand doesn’t drop suddenly when prices rise, as people still need to buy them to live. The planting, growing and harvesting of crops don’t adjust rapidly to price changes. Global grain markets are dominated by a few exporting regions such as the Black Sea, disruption to which has a huge effect on prices. Big players hold sway over many agricultural products, and speculative activity amplifies swings in prices.