Download perfect competition - the economics of competitive markets

perfect competition - the economics of
competitive markets
Introduction
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 marketclearing 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 breakeven 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.