The purpose of descriptive or positive economics is to study what is. Models are used to derive the theories, laws and principles which can be observed in the relationship between economic agents. Often the relationships are stated in mathematical terms and with the use of graphs. Two events which change in the same direction are said to be directly related (and inversely related if they change in opposite direction).
|The economist will, for instance, try to identify the factors which explain why firms wish to hire employees. That may be, for instance, the need to sell more products.