2.1 - Rational Decision Making
The concept of the margin in economics
The margin refers to the change in one variable resulting from a one-unit increase in another variable. This idea is central to many economic theories, as it assumes that people often make decisions based on small, incremental changes rather than all-or-nothing choices.
Key aspects of the margin
The margin measures the additional effect caused by producing, consuming, or changing one extra unit of something. Marginal cost is the extra cost of producing one more unit of a good - for example, it represents the cost added by the last item made.
Economic theory suggests individuals decide on actions like working an extra hour by weighing the marginal benefits against the marginal costs, rather than deciding on total work time.
Applications of the margin include:
- Price and wage differences between markets or jobs
- Externalities, such as the additional social costs or benefits of an action
- Profit-maximising output in markets like perfect competition
- Efficiency in market structures, including monopolies
- Marginal utility and rational behaviour in consumption
Calculating marginal cost
Where:
- Total cost at new output level = Overall cost of producing the increased quantity (£)
- Total cost at previous output level = Overall cost before the increase (£)
Worked example - Calculating marginal cost
The total cost of producing 350 items is £750, and the total cost of producing 351 items is £758. Calculate the marginal cost of the 351st item.
Step 1: Identify the values
- Total cost at 351 items = £758
- Total cost at 350 items = £750
Step 2: Apply the marginal cost formula
Step 3: Interpretation
The additional cost of producing the 351st item is £8, showing the incremental expense for one more unit.
Economic agents as utility maximisers
Traditional economic theory views economic agents, such as producers, consumers, and workers, as seeking to maximise their utility. Utility refers to well-being, happiness, or satisfaction gained from actions or resources.
Ways economic agents maximise utility
Agents are assumed to make decisions purely to achieve the highest possible utility, ignoring other influences. However, utility maximisation varies by agent:
- Consumers aim to increase personal satisfaction from goods and services
- Producers focus on boosting profits to ensure business success
- Workers seek to balance high earnings with sufficient leisure time
How consumers act rationally
Rational consumers make choices to maximise utility while staying within their budget. This involves understanding how satisfaction changes with each additional item consumed.
Key concepts in rational consumption
- Marginal utility - The extra satisfaction gained from one more unit of a good
- Total utility - The overall satisfaction from all units of a good consumed
- Law of diminishing marginal utility - Each successive unit provides less additional satisfaction than the previous one. For instance, the first slice of cake might bring high enjoyment, but the fifth slice offers much less
Rational consumption point
A rational consumer buys a good up to the point where marginal utility equals the price. For example, if the satisfaction from a banana is worth 60p, the consumer will pay 60p for it, but only 35p for a second banana if its marginal utility is lower.
This diminishing marginal utility explains downward-sloping demand curves, as consumers are willing to pay less for extra units.
Economic objectives of different agents
Economic agents often aim to maximise specific outcomes, though objectives can vary. Traditional assumptions focus on maximisation, but other goals like ethics or stability may also apply.
Objectives of producers
Producers typically seek to maximise profit, calculated as total revenue minus total costs. Revenue comes from sales, while costs include all production expenses.
Reasons for profit maximisation:
- Ensures survival, as ongoing losses can force closure
- Allows rewards for owners, shareholders, or staff
- Enables reinvestment for growth or expansion
Alternative objectives:
- Maximising sales or market share to gain monopoly power and charge higher prices
- Building prestige to attract top talent
- Pursuing ethical goals, such as sourcing locally to support communities, even if it raises costs
Objectives of consumers
Consumers aim to maximise utility without exceeding their income, focusing on choices that provide the most satisfaction.
Personal utility factors vary by individual, such as prioritising security through savings or enjoyment from luxuries like travel. As workers, consumers seek to maximise earnings while maintaining desired leisure time.
Objectives of governments
Governments aim to maximise public interest by balancing national resources with population needs.
Key government objectives:
- Economic growth, measured by increases in GDP
- Full employment, ensuring all able workers have jobs
- Balance of payments equilibrium, matching inflows and outflows of money
- Low inflation to control price rises and avoid economic issues
These goals often conflict; for example, spending to create jobs might increase inflation.