The term demand signifies the ability or the willingness to buy a particular commodity at a given point of time. Economists record demand on a demand schedule and plot it on a graph as a demand curve that is usually downward sloping. The downward slope reflects the relationship between price and quantity demanded as price decreases quantity demanded increases. The simplest economic growth models take income per capita as the measure of well being. A straight forward generalization would add numerous other components to the welfare criterion aside from income.