In microeconomics, supply and demand is an economic model of price determination in a market. By contrast, responses to changes in the price of the good are represented as movements along unchanged supply, a supply schedule is a table that shows the relationship between the price of a good and the quantity supplied. Under the assumption of perfect competition, supply is determined by marginal cost and that is, firms will produce additional output while the cost of producing an extra unit of output is less than the price they would receive. A hike in the cost of raw goods would decrease supply, shifting costs up, while a discount would increase supply, shifting costs down, by its very nature, conceptualizing a supply curve requires the firm to be a perfect competitor. This is true because each point on the curve is the answer to the question If this firm is faced with this potential price, how much output will it be able to. Economists distinguish between the curve of an individual firm and between the market supply curve. The market supply curve is obtained by summing the quantities supplied by all suppliers at each potential price, thus, in the graph of the supply curve, individual firms supply curves are added horizontally to obtain the market supply curve. Economists also distinguish the market supply curve from the long-run market supply curve. In this context, two things are assumed constant by definition of the run, the availability of one or more fixed inputs. In the long run, firms have a chance to adjust their holdings of physical capital, furthermore, in the long run potential competitors can enter or exit the industry in response to market conditions. For both of these reasons, long-run market supply curves are generally flatter than their short-run counterparts, the determinants of supply are, Production costs, how much a goods costs to be produced. Production costs are the cost of the inputs, primarily labor, capital, energy and they depend on the technology used in production, and/or technological advances. Following the law of demand, the curve is almost always represented as downward-sloping, meaning that as price decreases. Just like the supply curves reflect marginal cost curves, demand curves are determined by marginal utility curves, the demand schedule is defined as the willingness and ability of a consumer to purchase a given product in a given frame of time. It is aforementioned, that the curve is generally downward-sloping. Two different hypothetical types of goods with upward-sloping demand curves are Giffen goods, by its very nature, conceptualizing a demand curve requires that the purchaser be a perfect competitor—that is, that the purchaser has no influence over the market price. This is true because each point on the curve is the answer to the question If this buyer is faced with this potential price. If a buyer has market power, so its decision of how much to buy influences the price, then the buyer is not faced with any price
Image: Fig 5 Supply and demand curves
The price P of a product is determined by a balance between production at each price (supply S) and the desires of those with purchasing power at each price (demand D). The diagram shows a positive shift in demand from D1 to D2, resulting in an increase in price (P) and quantity sold (Q) of the product.