[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.
Product supply lines are affected by factors such as weather, natural disasters and the cost of fuel. When your product supply is affected, so is the way you market your products. If supply costs suddenly double due to political issues abroad, you may have to change your marketing from a price-focused approach.