[Note: The distance between cities in California (US) distance chart below is straight line distance (may be called as flying or air distance) between the two locations in California (US) calculated based on their latitudes and longitudes. This distance may be very much different from the actual travel distance.]
In drawing the demand schedule or the demand curve for a good we take income of the people as given and constant. When as a result of the rise in the income of the people, the demand increases, the whole of the demand curve shifts upward and vice versa. The greater income means the greater purchasing power.
Elasticity is the strength of the relationship between price levels and consumer demand. A product is highly elastic if consumer demand varies considerably with price. For these products, an increase in price is likely to cause a substantial downward change in the quantity of demand. The prices of inelastic products, by contrast, do not vary considerably with price. For inelastic products, either increases or decreases in price are unlikely to change the quantity of consumer demand.