Advice on drawing diagrams in the exam •
The right size for a diagram is about 1/3 of a side of A4 – don’t make them too small – if needed, move onto a new side of paper rather than trying to squeeze a diagram in at the bottom of a page
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Avoid wrapping text around the diagram – keep the text separate and leave a line between the text and your page
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Avoid directional arrows they clutter up the diagram and add little to it
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Remember to label each curve clearly so that it is clear which curves are shifting
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Remember to label carefully and accurately both the x and the y axis
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Always draw dotted lines to the x and y axis to show changing prices, quantities etc.
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Draw in pencil and always remember to use a rule, freehand diagrams are untidy
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Draw diagrams to the right technical level, don’t resort to simple supply and demand analysis when more complex cost and revenue curves are required (remember that this is A2)
Diagrams included in this revision document 1. The law of diminishing returns 2. Fixed and variable costs in the short run 3. Changes in variable costs and the effect on the profit maximising price, output and profit 4. The long run minimum efficient scale 5. Economies and diseconomies of scale in long run production and the effect on profits 6. A natural monopoly and economic efficiency 7. Understanding average, marginal and total revenue 8. Different objectives of businesses – effect on price, output and profit 9. The shut down price for a business in the short run 10. Short and long run in perfect competition and comparison with pure monopoly 11. Entry barriers for a monopolist and economies of scale with a monopoly 12. Price discrimination (i) peak and off-peak pricing (ii) 3rd degree discrimination 13. Oligopoly – the kinked demand curve model 14. Game theory – price collusion and the economics of a cartel 15. Elasticity of demand and pricing power for a business in imperfect competition
The short run is defined in economics as a period of time where at least one factor of production is assumed to be in fixed supply i.e. it cannot be changed. In the short run, the law of diminishing returns states that as we add more units of a variable input (i.e. labour or raw materials) to fixed amounts of land and capital, the change in total output will at first rise and then fall.
Total Output (Q)
(Q) Slope of the curve gives the marginal product of labour Diminishing returns are apparent here – total output is rising but at a decreasing rate I.e. the marginal product of labour is increasing
Units of Labour Employed (L) It is now widely recognised that the effects of globalisation, and in particular the ability of trans-national corporations to source their factor inputs from more than one country and engage in rapid transfers of business technology and other information, makes the concept of diminishing returns less relevant in the real world of business. In many industries as a business expands, it is more likely to experience increasing returns leading to lower unit costs of production.
Fixed and variable costs in the short run
Fixed costs (FC) are independent of output and must be paid out even if the production stops. Capital intensive industries with a high ratio of fixed to variable costs offer scope for economies of scale. AFC = Fixed Costs (FC) / Output (Q). Costs
£2000
Total Fixed Cost
£1000
Average Fixed Cost 10
Costs
Output (Q)
20
Marginal Cost (MC)
Average Total Cost (AC)
Average Variable Cost (AVC)
Average Fixed Cost Output (Q)
These are the “traditional” short run cost curves Notice that marginal cost cuts both AVC and ATC at the minimum point of each You don’t have to prove this in the exam but your diagrams need to be accurate so it is worth practising them as often as possible to improve your accuracy
Changes in variable costs and the effect on the profit maximising price; output and profit Important: A rise in fixed costs has no effect on marginal cost – it simply causes an upward shift in the average cost curve. But a rise in variable cost causes a shift in both MC and AC Costs
MC1 AC2
AC1
Output (Q)
Higher variable costs – the effect on equilibrium prices and profits (ceteris paribus) Profit after cost rise
Costs
MC1 AC2
P2 P1 AC1
AC2
AC1
MR Q2 Q1
AR Output (Q)
The long run minimum efficient scale of production (MES)
Cost per unit in the long run
In the long run, all factors of production are variable. How the output of a business responds to a change in factor inputs is called returns to scale. Economies of scale are the cost advantages exploited by expanding the scale of production in the long run. The effect is to reduce long run average costs over a range of output.
LRAC
Falling LRAC – Economies of Scale (Increasing Returns to Scale)
Rising LRAC – Diseconomies of Scale (Decreasing Returns to Scale)
Output (Q) MES
Costs per unit in the long run (ATC)
The minimum efficient scale (MES) is the scale of production where the internal economies of scale have been fully exploited. The MES corresponds to the lowest point on LRAC and is also known as an output range over which a business achieves productive efficiency. It is often a range of output and will differ from industry to industry as we can see from the diagram below.
LRAC1
LRAC1 - Low MES – characteristic of a competitive market LRAC2
LRAC3 LRAC3 - High MES – characteristic of a natural monopoly
MES1
MES2
Output (Q)
MES3
Economies and diseconomies of scale in long run production and the effect on profits Deriving the long run average cost curve – the envelope of a series of short run average cost curves Costs SRAC1
SRAC3
SRAC2 AC1
LRAC AC2 AC3
Q1
Costs
Q2
Q3
MC1
Output (Q)
Profit at Price P1 Profit at Price P2 SRAC1
P1
Lower costs allows a profit maximising firm to charge a lower price (P2) but make higher total profits because of the fall in AC per unit
P2
SRAC3 MC2
AR (Demand) MR Q1
Q2
Output (Q)
A natural monopoly and economic efficiency
Profit at price P1
Revenue Cost and Profit
Loss at price P2
P1
AC1 LRAC
AC2
LRMC P2 Demand (AR) MR Q1
Q2
Output (Q)
A natural monopoly – splitting infrastructure from the final delivery of services A natural monopoly occurs in an industry where LRAC falls over a wide range of output levels such that there may be room only for one supplier to fully exploit all of the internal economies of scale, reach the minimum efficient scale and therefore achieve productive efficiency. The major utilities such as gas, electricity and water are often put forward as examples of industries with strong "natural tendencies" towards being a natural monopoly in part because of the huge fixed costs of building and maintaining nationwide networks / infrastructures of cables and pipes. In fact we can make an important distinction between the supply and distribution of services such as gas and electricity and internet services. Often a monopolistic firm is in charge of maintaining a network but a regulator will seek to inject competition into the market by allowing new firms to come in a use the existing network and compete for customer contracts in the delivery of services. Good examples include the liberalisation of postal services and also the decision by OFCOM to force British Telecom to open up its networks to household and business customers so that rival firms can compete for the market demand in telecommunication services.
Understanding average, marginal and total revenue Total revenue is maximised when MR = 0
Revenue
Total Revenue (TR)
Ped >1 for a price fall along this length of AR
Price elasticity of demand = 1 at this output
Average Revenue (Demand) AR
Marginal Revenue (MR)
Output (Q)
Average and marginal revenue
Total revenue is maximised at price P1 where marginal revenue is zero
P2
A rise in price to P2 causes a reduction in total revenue P1
AR (Demand)
Total revenue at price P2
Q2
Output (Q)
Q1
MR
Different objectives of businesses – effect on price, output and profit Costs Profit Max at Price P1 Revenue Max at Price P2 SRAC MC
P1 P2
AC1 AC2 P3 AR (Demand)
Q1
Q2
MR
Q3
Output (Q)
It is now widely accepted that modern businesses depart frequently from pure profit maximisation pricing strategies as part of competition within markets. The objectives and strategies of firms will vary with market conditions and with the aims of the different stakeholders that are part of the decision-making process in modern corporations. The normal profit maximising output is at Q1 (where marginal revenue = marginal cost) Total revenue is maximised at output Q2 where marginal revenue is zero. This gives a lower level of total profits, although supernormal profits are still being earned. If shareholders insist on the business achieving a normal rate of profit as a minimum then the managers of a business have the discretion to vary price anywhere above P3 At any output beyond Q3 (where average revenue and average cost intersect) losses are made (i.e. sub-normal profits). Be aware of the reasons for firms moving away from profit maximisation and also the effects of different price strategies on consumer and producer welfare and economic efficiency.
The shut down price for a business in the short run ATC
MC = supply Costs, Revenues
AVC
P2
P2
Break-Even Price
P1 The Shut Down Price
Q1
Output (Q)
The shut down price for a business in the short run The theory of the firm assumes that a business needs to make at least normal profit in the long run to justify remaining in an industry but this is not a strict requirement in the short term. In the short run the firm will continue to produce as long as total revenue covers total variable costs or put another way, so long as price per unit > or equal to average variable cost (AR = AVC). The reason for this is as follows. A business’s fixed costs must be paid regardless of the level of output. If we make an assumption that these costs are sunk costs (i.e. they cannot be covered if the firm shuts down) then the loss per unit would be greater if the firm were to shut down, provided variable costs are covered. In the short run, the supply curve for a competitive firm is the marginal cost curve above average variable cost.
Short and long run in perfect competition No barriers to entry and super normal profits encourage the entry of new firms shifting market supply & price downward until price falls back to P2. Normal profits are restored. Market Demand and Supply Price (P)
Individual Firm’s Costs and Revenues
Price (P) MC (Supply) Market Supply (MS) AR1 = MR1
P1 P1
AC
MS2 P2
P 2
AR2 = MR2 Long run equilibrium output
Market Demand
Q1
Q2
P2
Output (Q)
Output (Q)
Q3
Competitive Market
Pure Monopoly
Price (P)
Price (P)
Market Supply
Market Supply
P mon P comp
Monopoly Demand
Market Demand MR Q1
Q2
Q1
Output (Q)
Entry barriers for a monopolist and monopoly with economies of scale
Revenue Cost and Profit
A P1 AC = MC (Potential Entrant into the market)
D
B
C
Pc
Monopoly Demand (AR)
MR Q1
LRAC = LRMC (Existing Monopolist)
Qc
Competitive Market
Output (Q) Pure Monopoly
Price (P)
Price (P)
Competitive Supply (MC)
Market Supply
P comp Monopoly Supply with Scale Economies
P mon
Monopoly Demand
Market Demand MR Q1
Q1 Q2
Output (Q)
Price discrimination (i) peak and off-peak pricing (ii) 3rd degree discrimination Price (P) and Costs
Supply (Marginal Cost)
Price Peak
Price Off-Peak
Peak Demand
MR Peak
Off-Peak Demand MR Off-Peak Output Off-Peak
Output
Output Peak
Market A Pric e
Market B Pric e
Profit from selling to market A – with a relatively elastic demand – and charging a lower price
Demand in segment B of the market is relatively inelastic. A higher unit price is charged
P b
P a
MC=AC
MC=A C
ARa
MR a
Q a
MR b Quantit y
Q b
AR b Quantit y
Oligopoly – the kinked demand curve model Costs Revenues
Raising price above P1 Demand is relatively elastic Firm loses market share and some total revenue
Assume we start out at P1 and Q1: Will a firm benefit from raising price above P1? Will it benefit from cutting price below P1?
MC1
P1
Reducing price below P1 Demand is relatively inelastic Little gain in market share – other firms have followed suit Total revenue may still fall
AR Q1
Output (Q)
MR
An oligopoly is a market dominated by a few producers, each of which has control over the market. It is an industry where there is a high level of market concentration. However, oligopoly is best defined by the conduct (or behaviour) of firms within a market rather than its market structure. The kinked demand curve model assumes that a business might face a dual demand curve for its product based on the likely reactions of other firms in the market to a change in its price or another variable. The common assumption is that firms in an oligopoly are looking to protect and maintain market share and that rival firms are unlikely to match another’s price increase but may match a price fall. I.e. rival firms within an oligopoly react asymmetrically to a change in the price of another firm. The kinked demand curve model therefore makes a prediction that a business might reach a stable profit-maximizing equilibrium at price P1 and output Q1 and have little incentive to alter prices. Even a shift in the marginal cost curve (MC1) in the diagram above might not be enough to change the profit maximizing equilibrium. The kinked demand curve model predicts periods of relative price stability under an oligopoly with businesses focusing on non-price competition as a means of reinforcing their market position and increasing their supernormal profits.
Game theory – price collusion and the economics of a cartel
Individual Firm
Industr y M C
A C
P(cartel )
P(cartel )
MC (industry)
A C
Deman d M R Quot a
Firms Output
Industr y Output
Collusion is a desire to achieve joint-profit maximization within a market or prevent price and revenue instability in an industry. Price fixing represents an attempt by suppliers to control supply and fix price at a level close to the level we would expect from a monopoly. To fix prices, the producers in the market must be able to exert control over market supply. In the diagram below a producer cartel is assumed to fix the cartel price at output Qm and price Pm. The distribution of the cartel output may be allocated on the basis of an output quota system or another process of negotiation. Although the cartel as a whole is maximizing profits, the individual firm’s output quota is unlikely to be at their profit maximizing point. For any one firm, within the cartel, expanding output and selling at a price that slightly undercuts the cartel price can achieve extra profits. Unfortunately if one firm does this, it is in each firm’s interests to do exactly the same. If all firms break the terms of their cartel agreement, the result will be an excess supply in the market and a sharp fall in the price. Under these circumstances, a cartel agreement might break down. Collusive behaviour is often predicted by game theory Game theory is concerned with predicting the outcome of games of strategy in which the participants (for example two or more businesses competing in a market) have incomplete information about the others' intentions. Collusive behaviour reduces some of the uncertainty that is characteristic of oligopolistic markets.
Elasticity of demand and pricing power for a business in imperfect competition
Price and Costs
Low Price Elasticity of Demand
MC
Price and Costs
Low Price Elasticity of Demand
MC
SRAC
SRAC
P1
P1 AC1
AC1 AR (Contestable market) MR MR
AR (Monopoly)
Q1
Q2
Output (Q)
The importance of price elasticity of demand in theory of the firm Price elasticity of demand is a concept that was introduced at AS level. Horizontal synopticity requires you to apply the concept in theory of the firm diagrams. A good example of when this can be done is on questions on contestable markets Highly contestable markets Baumol defined contestable markets as existing where “an entrant has access to all production techniques available to the incumbents, is not prohibited from wooing the incumbent’s customers, and entry decisions can be reversed without cost.” For a contestable market to exist there must be low barriers to entry and exit so that there is always the potential for new suppliers to come into a market to provide fresh competition to existing suppliers. For a perfectly contestable market, entry into and exit out of the market must be costless. When a market is contestable there are likely to be a large number of competing suppliers; the cross-price elasticity of demand will be high because of strong substitution effects when relative prices in a market change. Hence we can draw the average revenue curve to be price elastic. This reduces the potential for a business to charge a price that is well above the marginal cost of production. Profit margins are lower, output is higher and consumer welfare is great than it would be with a monopolist exploiting an inelastic demand curve (see left hand diagram).
