Economics Cambridge A Level Notes

Overview of the Syllabus

Chapter 30: Utility

Learning Objectives

Define total utility and marginal utility.
Calculate total utility and marginal utility.
Explain diminishing marginal utility.
Explain the equi-marginal principle.
Derive an individual demand curve.
Evaluate the limitations of marginal utility and assumptions of rational behavior.

30.1 Utility and Diminishing Marginal Utility

Utility: The satisfaction derived from consumption, measured in units (utils).
Marginal Utility (MU): Additional utility derived from the consumption of one more unit. $MU = \frac{\Delta TU}{\Delta Q}$
Total Utility (TU): Overall satisfaction derived from consuming all units of a good over time.
Law of Diminishing Marginal Utility: States that as more of a good is consumed, the additional satisfaction derived from each extra unit decreases.
- Example:
- 1st slice of pizza: Willing to pay $\$5$ , yields 10 units.
- 2nd slice: Willing to pay $\$4$ , yields 7 units.
- 3rd slice: Willing to pay $\$3$ , yields 3 units.
Consumers optimize purchasing behavior based on equating the marginal utility per dollar spent across all goods.

30.2 The Equi-Marginal Principle

A consumer maximizes utility when: $\frac{MUx}{Px} = \frac{MUy}{Py}$
Example Analysis ( $Px = \$1$ , $Py = \$2$ , Budget = $\$10$ ):
| Q | $MUx$ | $MUx / Px$ | $MUy$ | $MUy / Py$ |
| :--- | :--- | :--- | :--- | :--- |
| 1 | 60 | 60 | 50 | 25 |
| 2 | 40 | 40 | 44 | 22 |
| 3 | 25 | 25 | 36 | 18 |
| 4 | 18 | 18 | 20 | 10 |
| 5 | 14 | 14 | 14 | 7 |
Allocation: Consumer buys 4 units of X ( $\$4$ ) and 3 units of Y ( $\$6$ ).
Check: $\frac{MUx}{Px} = 18$ and $\frac{MUy}{Py} = 18$ . Total Utility = $(60 + 40 + 25 + 18) + (50 + 44 + 36) = 273$ utils.

30.3 Derivation of an Individual Demand Curve

The price a consumer is willing to pay corresponds to the MU of that unit. As MU falls, the price the consumer is willing to pay falls, creating a downward-sloping demand curve.

30.4 Limitations of Marginal Utility Theory

Measurement: Difficulty in quantifying utility (cardinal measurement).
Rationality: Assumptions of perfect information and constant calculation.
Income/Substitution Effects: Changes in price affect real income, not just relative price.

Chapter 31: Indifference Curves and Budget Lines

31.1 Indifference Curves

Shows combinations of two goods that give the same level of satisfaction.
Marginal Rate of Substitution (MRS): The rate at which a consumer is willing to substitute one good for another. $MRS = \frac{\Delta Qy}{\Delta Qx}$ .

31.2 Budget Line

Represents all combinations of goods affordable with a fixed income ( $I$ ). Equation: $I = (Px \cdot Qx) + (Py \cdot Qy)$ .
Shifts outward with increased income; rotates with price changes.

Chapter 32: Efficiency and Market Failure

32.1 Economic Efficiency

Productive Efficiency: Producing at the lowest point on the ATC curve ( $P = MC$ is not a requirement here, but $ATC$ is minimized).
Allocative Efficiency: $P = MC$ . Resources are allocated according to consumer preferences.
Pareto Optimality: No one can be made better off without making someone else worse off.

32.2 Market Failure

Occurs when social welfare is not maximized. Causes include:
- Externalities: Divergence between private and social costs/benefits.
- Public Goods: Non-excludable and non-rivalrous.
- Information Asymmetry: One party lacks knowledge (Adverse Selection/Moral Hazard).

Chapter 33: The Labor Market

33.1 Demand for Labor

Marginal Revenue Product (MRP): The extra revenue a firm gains by employing one more worker. $MRP = MPP \cdot MR$ , where $MPP$ is Marginal Physical Product.
Factors shifting demand: Productivity, price of the final product, and cost of capital (substitutes).

33.2 Supply of Labor

Determined by workers' trade-off between leisure and wages.
Substitution Effect: Higher wages make leisure more expensive, leading to more work.
Income Effect: Higher wages increase income, leading to a demand for more leisure (backward-bending supply curve).

33.3 Wage Determination

Perfect Competition: Wage is set by the market where $DL = SL$ .
Monopsony: A single buyer of labor. They hire where $MRP = MCL$ (Marginal Cost of Labor).

Chapter 34: Government Intervention in the Microeconomy

34.1 Correcting Market Failure

Indirect Taxes: To correct negative externalities (e.g., carbon tax). Shifts supply curve left.
Subsidies: To encourage positive externalities (e.g., education). Shifts supply curve right.
Direct Provision: Providing public goods (national defense).

34.2 Price Controls

Maximum Price (Ceiling): Set below equilibrium to help consumers; can lead to shortages.
Minimum Price (Floor): Set above equilibrium (e.g., Minimum Wage); can lead to surpluses.

Chapter 35: The Macroeconomy: Measurement

35.1 National Income Statistics

Gross Domestic Product (GDP): Total value of goods/services produced in a country in a year.
Gross National Income (GNI): $GDP$ plus net income from abroad.
Real vs. Nominal: $Real GDP = \frac{Nominal GDP}{GDP Deflator} \cdot 100$ .

35.2 PPP (Purchasing Power Parity)

Adjusts GDP to reflect the different costs of living and inflation rates in different countries.

Chapter 36: Circular Flow of Income and AD/AS

36.1 Circular Flow

Injections (J): Investment ( $I$ ), Government Spending ( $G$ ), Exports ( $X$ ).
Leakages (W): Savings ( $S$ ), Taxes ( $T$ ), Imports ( $M$ ).
Equilibrium occurs when $J = W$ .

36.2 Aggregate Demand (AD)

$AD = C + I + G + (X - M)$ .
The downward slope is due to the wealth effect, interest rate effect, and international trade effect.

36.3 Aggregate Supply (AS)

Short-run (SRAS): Upward sloping, influenced by costs of production (wages, raw materials).
Long-run (LRAS): Vertical (Classical view) or curved (Keynesian view) representing the full employment level of output ( $Y_f$ ).