In a market economy, price is determined by the interaction of supply and demand. The study of supply and demand is also known as the study of fundamentals or "fundamental analysis". In this section you will learn how to estimate a market price for commodities using the law of supply and demand as reflected in the "stocks to use ratio". The stocks to use ratio is a closely watched figure in when establishing asking prices for commodities. In order to understand stocks to use, you must understand the economic theory of supply and demand. Supply and demand graphs are useful tools used to illustrate this concept.