7.21 - Different Market Structures
The meaning and characteristics of market structures
Market structure refers to the way in which goods and services are provided by firms within a specific market. It helps economists analyse how markets function and how firms behave in different environments.
Key characteristics that define market structures
- Number of buyers and sellers - This determines the level of competition.
- Nature of products - Products can be identical, differentiated, or unique.
- Ease of entry - Barriers influence whether new firms can join the market easily.
- Information availability - The amount of knowledge accessible to buyers and sellers impacts decision-making.
Economists use models of market structures as idealised examples to compare real-world markets against theoretical benchmarks.
Types of market structures
Markets can be categorised into different structures based on their competitive nature. These range from highly competitive to those dominated by few or single firms.
Perfect competition
This structure features many firms producing identical products with no barriers to entry. Firms have freedom of entry into the industry and all participants have perfect information.
Monopolistic competition
Many firms offer differentiated products with some freedom to set prices. Firms act as price makers with some control over product and price.
Oligopoly
A few dominant firms control the market, often with high barriers to entry. Firms can erect barriers to entry using market power, products vary widely, and price control depends on competitors' actions.
Monopoly
A single firm supplies the entire market, protected by substantial barriers. This can be a pure monopoly (one firm for the entire market) or a monopolistic industry (one firm with dominant market share). Barriers include patents and other restrictions.
Natural monopoly
Occurs when a single firm can supply the market more efficiently due to falling long-run average costs. Long-run average costs decrease with a single firm, making multiple firms inefficient.
How to identify market structures using concentration ratios
To determine a market's structure, economists examine indicators like the number of firms and market concentration.
Methods for identifying market structures
- Counting the number of firms - A higher number suggests closeness to perfect competition.
- Assessing concentration ratios - Measures the market share of the largest firms.
- Evaluating ease of entry and exit - Low barriers indicate more competition.
- Considering economies of scale - Important in structures like natural monopolies.
Formula for concentration ratio
The concentration ratio shows the combined market share of the top firms as a percentage.
Where:
- Market size of top firms = Combined output or revenue of the largest firms (e.g., top 4)
- Total size of market = Overall output or revenue in the market
A higher percentage points towards oligopoly or monopoly.
Worked example - Calculating a 4-firm concentration ratio
In a market with a total revenue of £400 million, the top four firms have revenues of £100 million, £90 million, £70 million, and £60 million. Calculate the 4-firm concentration ratio.
Step 1: Identify the values
- Market size of top 4 firms = £100m + £90m + £70m + £60m = £320 million
- Total size of market = £400 million
Step 2: Apply the concentration ratio formula
Step 4: Interpretation
An 80% ratio indicates high concentration, suggesting the market is closer to an oligopoly.
The spectrum of competition in markets
Markets do not always fit neatly into one structure but exist on a continuum from highly competitive to non-competitive.
Features of the competition spectrum
- Highly competitive end - Characterised by many firms and low barriers to entry, resembling perfect competition.
- Less competitive end - Features few firms and high barriers to entry, approaching monopoly.