(2) less than aggregate demand Explanation: If the supply is less than the demand, the price will increase. Inflation, the persistent increase in the average price level, can be caused by an increase in aggregate demand or a decrease in aggregate supply. This suggests two basics sources, causes, or types of inflation—demand-pull inflation and costpush inflation. In general, prices increase as a result of market shortages, which occur when quantity demanded exceeds quantity supplied. Market shortages can be created by either increases in demand or decreases in supply. Translating this to the macro-economy suggests that inflation occurs when aggregate demand exceeds aggregate supply.