What Factors Affect Demand?The Ceteris Paribus Assumption
A demand curve or a supply curve is a relationship between two, and only two, variables: quantity on the horizontal
axis and price on the vertical axis.Willingness to purchase suggests a desire, based
on what economists call tastes and preferences.Professors are usually able to afford better housing and transportation
than students, because they have more income.The assumption behind a demand curve or a supply curve is that no relevant
economic factors, other than the product's price, are changing.We defined demand as the amount of some product a consumer is willing and able to purchase at each price.If you neither need nor want something, you will not buy it. Ability
to purchase suggests that income is important.Exactly how do these various factors affect
demand, and how do we show the effects graphically?To answer those questions, we need the ceteris paribus
assumption.