Differing objectives and policies of firms (incl. price discrimination)

Economics· Unit 2, Section 3.3: Firm behaviour· 45 min read

1. Traditional and Alternative Firm Objectives★★☆☆☆⏱ 10 min

The traditional model assumes firms maximise profit, but modern separated ownership and control (where shareholders own the firm and managers run it) creates a principal-agent problem that leads to alternative objectives.

📘 Definition

Principal-agent problem

A conflict of interest where agents (managers) pursue their own goals rather than the principals' (shareholders') goal of maximum profit.

Profit maximisation: The long-run default objective for most small, owner-run firms
Sales revenue maximisation: Managers aim to maximise total firm revenue to earn performance bonuses linked to firm size
Sales maximisation: Firms maximise market share to gain first-mover advantages and reduce new competition
Satisficing: Managers balance competing stakeholder demands to hit acceptable, not maximum targets

📐 Worked Example

A firm faces a total cost function $T C = 200 + 10 Q$ and total revenue function $T R = 50 Q - 0.5 Q^{2}$ . Find the profit maximising and revenue maximising output levels.

1
First, calculate profit maximising output using MC = MR:
2
$MC = \frac{dTC}{dQ} = 10, \quad MR = \frac{dTR}{dQ} = 50 - Q$
3
$10 = 50 - Q \implies Q_{\pi max} = 40$
4
Next, calculate revenue maximising output using MR = 0:
5
$MR = 50 - Q = 0 \implies Q_{R max} = 50$

✓ Quick check

Test your understanding of the principal-agent problem:

Which of the following is a direct consequence of the principal-agent problem?
- Firms always maximise long run profit
- Managers may prioritise firm size over maximum shareholder returns
- Perfectly competitive firms earn zero abnormal profit in the long run
- Price discrimination reduces total consumer surplus
Reveal answer
Managers may prioritise firm size over maximum shareholder returns —
This is the core conflict between manager goals and shareholder profit goals.

2. Pricing and Output for Non-Profit Maximising Firms★★★☆☆⏱ 12 min

Each objective produces a distinct output and price point that can be plotted on a standard average cost / average revenue diagram. For constrained sales maximisation, the firm will produce at the point where AR = ATC, but only if it meets a pre-set minimum profit requirement.

\text{Profit Maximisation: } MC = MR \implies P_{\pi max} > P_{R max} \text{ and } Q_{\pi max} < Q_{R max}

📐 Worked Example

Using the earlier TC and TR functions, calculate the price at the revenue maximising output level Q=50.

1
First derive the average revenue (demand) function from total revenue:
2
$TR = P \times Q = 50Q - 0.5Q^2 \implies P = 50 - 0.5Q$
3
Substitute Q=50 into the demand function:
4
$P = 50 - 0.5(50) = 25$

3. Conditions and Types of Price Discrimination★★★☆☆⏱ 15 min

📘 Definition

Price Discrimination

A firm with market power charges different prices to separate groups of customers for identical units of a good, with no corresponding difference in production costs.

The firm must have sufficient market power to set prices above marginal cost
The firm can separate customers or markets at low cost, preventing resale (arbitrage) between groups
Different customer groups have different price elasticities of demand

Degree	Description	Real World Example
First Degree	Firm charges each customer their exact maximum willingness to pay	Independent car dealership haggling over individual prices
Second Degree	Firm uses self-selection to segment customers via quantity discounts	Supermarket multi-buy offers for larger product packs
Third Degree	Firm explicitly segments customers into distinct, identifiable markets	Student discounts for cinema tickets, peak/off-peak train fares

📐 Worked Example

A monopolist operates two separate markets with price elasticities of demand of -2 and -4. The marginal cost of production is $12. Use the inverse elasticity pricing rule to find the optimal price in each market.

1
The inverse elasticity rule states $P = \frac{M C}{1 + \frac{1}{P E D}}$
2
For market 1, PED = -2:
3
$P_1 = \frac{12}{1 - 0.5} = 24$
4
For market 2, PED = -4:
5
$P_2 = \frac{12}{1 - 0.25} = 16$

4. Welfare Impacts of Price Discrimination★★★★☆⏱ 8 min

Price discrimination transfers consumer surplus to producers, but can also increase total market output, potentially raising total social surplus relative to a single-price monopoly.

🔬 Derivation

Goal:

Compare total surplus under single pricing vs third degree price discrimination

Starting from:

Single price monopoly sets P above MC, restricts output below the socially optimal level

1
Under third degree price discrimination, the firm can lower prices in the elastic demand market, raising total output
2
If the firm would not supply the low-demand market at all under single pricing, price discrimination makes that market available to consumers
3
Total producer surplus rises unambiguously, while consumer surplus may rise or fall depending on market conditions

Result:

Price discrimination is not always welfare reducing, and can in some cases be more socially efficient than single price monopoly.

5. Common Pitfalls

Wrong move:

Assuming all firms always maximise profit in all scenarios

Why:

This ignores the principal-agent problem that is explicitly tested in CIE 9708 exams

Correct move:

State your assumed firm objective clearly at the start of any analysis

Wrong move:

Confusing revenue maximisation with profit maximisation

Why:

Forgetting that revenue maximisation occurs at MR=0, not the MC=MR profit maximisation rule

Correct move:

Label both output points separately on all cost-revenue diagrams

Wrong move:

Claiming price discrimination requires different costs across markets

Why:

Pure price discrimination depends only on differing demand elasticities, not cost differences

Correct move:

Explicitly note that cost parity is the baseline assumption for pure price discrimination

Wrong move:

Stating price discrimination is always bad for consumers

Why:

Third degree price discrimination can open up new markets that would not exist under single pricing

Correct move:

Evaluate both consumer surplus losses and gains before drawing a final welfare conclusion

Wrong move:

Mixing up second and third degree price discrimination

Why:

Failing to distinguish between customer self-selection (2nd degree) and explicit market segmentation (3rd degree)

Correct move:

Use standard CIE-approved examples to categorise each type correctly in exam answers

6. Quick Reference Cheatsheet

Firm Objective	Output Rule	Key Outcome
Profit Maximisation	MC = MR	Maximum abnormal profit for shareholders
Sales Revenue Maximisation	MR = 0	Higher output, lower price than profit max
Constrained Sales Maximisation	AR = ATC (minimum profit constraint)	Maximum possible market share
Limit Pricing	P < potential entrant ATC	Blocks new market entry
First Degree Price Discrimination	P = MC for last unit sold	Captures 100% of consumer surplus

When this came up on past exams

AI-estimated based on syllabus patterns — cross-check with official past papers for accuracy. Use only as revision-focus signals.

2025 · 2
Price discrimination short answer question
2024 · 4
Alternative firm objectives essay
2023 · 2
Revenue vs profit maximisation calculation

What's Next

Mastering firm objectives and price discrimination gives you a robust framework to analyse real-world firm behaviour across oligopoly and monopolistic competition topics, which are heavily weighted in CIE Paper 4 extended essays. You will next apply these frameworks to game theory and oligopoly interdependence, where competing firm objectives directly shape collusive and non-collusive outcomes. This subtopic also links directly to government micro intervention policies, as regulators often assess price discrimination practices for consumer exploitation risks. Ensure you practice drawing fully labelled cost-revenue diagrams for each objective, as CIE examiners award up to 4 marks for accurate, correctly annotated diagrams in 12-mark responses.

→Monopolistic Competition