In recent years there has been a shift in demand on the part of overseas Canadian wheat buyers toward the Canada Prairie Spring varieties, away from the Hard Red Spring varieties. A decline in the preference for Hard Red Spring wheat shifts the demand curve inward, to the left, as illustrated in figure 5. With no reduction in supply, the effect on price results from a movement along the supply curve to a lower equilibrium price where supply and demand is once again in balance. In order for prices to increase producers will have to reduce the quantity of hard red spring wheat brought to the market place or find new sources of demand to replace the consumers who withdrew from the marketplace due to changing preferences or a shift in demand. Changes in supply and demand can be short run or long run in nature.
Weather tends to influence market prices generally in the short run.
Changes in consumer preferences can have either a short run or long run effect on prices depending upon the goods or services, for example whether they are luxuries or necessities. A luxury good may enjoy a short term shift in demand due to changing styles or snob appeal while necessities tend to have stable or long run demand curves. Another major factor influencing market prices is technology. A major effect of technology in agriculture is to shift out the supply curve rapidly by reducing the costs of production on a per unit basis. At the same time if total demand does not increase sufficiently to absorb the excess goods produced at lower costs, the long run impact of technology on the market place will be to lower prices.