If you have the desire to buy, but not with the power to buy or don't want to, but can be purchased. Not considered to be demand. Economic demand is effective demand, which means that a buyer is willing to buy one, I would like to be able to buy. Factors determining demand mean variables or factors that influence the amount of goods that consumers desire to buy (demand Quantity) of these factors will influence the purchase quantity is much less not equal. This all depends on the behavior of individual consumers and the passage of time. We can show the relationship between a purchase quantity defined as the symbols of algebra. Which is called the? Good command function (Demand Function) can be expressed as follows: