Supply and demand curves shift over time as market conditions change. In this example,rightward shifts of the supply and demand curves lead to a slightly higher price and a much larger quantity. In general,changes in price and quantity depend on the amount by which each curve shifts and the shape of each curve. Supply and demand curves shift over time as market conditions change. In this example, rightward shifts of the supply and demand curves lead to a slightly higher price and a much larger quantity. In general, changes in price and quantity depend on the amount by which each curve shifts and the shape of each curve