• A demand curve graph depicts the relationship between price of a commodity (the y-axis) and the quantity of that commodity that is demanded at that price (the x-axis). • Demand curve will shift to left or right as a result of change in any nonprice determinant of demand. Thus, normally there is no shift in demand curve when price of a commodity falls. • Several factors like rising income, change in population, changes in expectations and changes in tastes and preferences affect individual and market demand.