perfect competition - the economics of competitive markets
The degree to which a market or industry can be described as competitive depends in part on how many suppliers are seeking the demand of consumers and the ease with which new businesses can enter and exit a particular market in the long run.
The spectrum of competition ranges from highly competitive markets where there are many sellers, each of whom has little or no control over the market price - to a situation of pure monopoly where a market or an industry is dominated by one single supplier who enjoys considerable discretion in setting prices, unless subject to some form of direct regulation by the government.
In many sectors of the economy markets are best described by the term oligopoly - where a few producers dominate the majority of the market and the industry is highly concentrated. In a duopoly two firms dominate the market although there may be many smaller players in the industry.
Competitive markets operate on the basis of a number of assumptions. When these assumptions are dropped - we move into the world of imperfect competition. These assumptions are discussed below
Assumptions behind a Perfectly Competitive Market
1. Many suppliers each with an insignificant share of the market – this means that each firm is too small relative to the overall market to affect price via a change in its own supply – each individual firm is assumed to be a price taker
2. An identical output produced by each firm – in other words, the market supplies homogeneous or standardised products that are perfect substitutes for each other. Consumers perceive the products to be identical
3. Consumers have perfect information about the prices all sellers in the market charge – so if some firms decide to charge a price higher than the ruling market price, there will be a large substitution effect away from this firm
4. All firms (industry participants and new entrants) are assumed to have equal access to resources (technology, other factor inputs) and improvements in production technologies achieved by one firm can spill-over to all the other suppliers in the market
5. There are assumed to be no barriers to entry & exit of firms in long run – which means that the market is open to competition from new suppliers – this affects the long run profits made by each firm in the industry. The long run equilibrium for a perfectly competitive market occurs when the marginal firm makes normal profit only in the long term
6. No externalities in production and consumption so that there is no divergence between private and social costs and benefits
Short Run Price and Output for the Competitive Industry and Firm
In the short run the equilibrium market price is determined by the interaction between market demand and market supply. In the diagram shown above, price P1 is the market-clearing price and this price is then taken by each of the firms. Because the market price is constant for each unit sold, the AR curve also becomes the Marginal Revenue curve (MR). A firm maximises profits when marginal revenue = marginal cost. In the diagram above, the profit-maximising output is Q1. The firm sells Q1 at price P1. The area shaded is the economic (supernormal profit) made in the short run because the ruling market price P1 is greater than average total cost.
Not all firms make supernormal profits in the short run. Their profits depend on the position of their short run cost curves. Some firms may be experiencing sub-normal profits because their average total costs exceed the current market price. Other firms may be making normal profits where total revenue equals total cost (i.e. they are at the break-even output). In the diagram below, the firm shown has high short run costs such that the ruling market price is below the average total cost curve. At the profit maximising level of output, the firm is making an economic loss (or sub-normal profits)
The Effects of a change in Market Demand
In the diagram below there has been an increase in market demand (ceteris paribus). This causes an increase in market price and quantity traded. The firm's average revenue curve shifts up to AR2 (=MR2) and the profit maximising output expands to Q2. Notice that the MC curve is the firm's supply curve. Higher prices cause an expansion along the supply curve. Following the increase in demand, total profits have increased. An inward shift in market demand would have the opposite effect. Think also about the effect of a change in market supply - perhaps arising from a cost-reducing technological innovation available to all firms in a competitive market.
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