What does a high market share and strong brand tell you about how contestable a market is?

• →Contestability theory states that market behaviour is disciplined not by the number of existing firms but by the threat of potential entry — a contestable market has lowsunk costs and few entry and exit barriers.
• →A firm that holds a high market share and a powerful brand name signals the presence of substantial barriers to entry that undermine this threat. A dominant brand, such as Coca-Cola in the soft drinks market, creates strong consumer loyalty through years of advertising and product differentiation.
• →This means that a potential entrant would need to commit to very large sunk costs in marketing, brand-building, and distribution networks to compete for customers who already exhibit a strong brand preference for competitors.
• →Low profitability of firms entering the market reduces the likelihood that a hit-and-run entry strategy (entering to capture supernormal profit before quickly exiting) would succeed. Therefore, even if the existing firm earns persistently high supernormal profits, the market remains relatively non-contestable because the asymmetry in brand strength acts as a structural barrier.
• →Furthermore, a high market share may allow the incumbent firms to exploit economies of scale, setting prices that a new entrant with lower output cannot profitably match.
• →The evaluative point is that brand strength alone does not make a market entirely non-contestable — if sunk costs are genuinely low and regulatory barriers are absent, niche entrants may still change the incumbent's behaviour in specific segments.
• →The diagram below shows the effect of a market being more contestable, forcing incumbent firsm to lower their price from point A (profit max) claoser to point B (sales max)

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This diagram shows how the threat of entry in a contestable market disciplines incumbent firm behaviour. Even with few competitors, the possibility of hit-and-run entry forces the firm to price at or near normal profit (AR = AC), preventing the exploitation of monopoly power. Use this diagram to show the difference between a concentrated market structure and a competitive market outcome.

• →Contestability and sunk costs: A market is contestable to the degree that sunk costs are low. Brand-related advertising spend is a classic sunk cost — it cannot be recovered on exit — so high branding activity by incumbents directly reduces contestability for potential entrants.
• →Barriers to entry vs barriers to exit: Distinguishing these is important. A strong brand primarily raises the cost of entry; barriers to exit (such as specialised capital) matter separately. Examiners reward students who treat these as distinct concepts rather than conflating them.
• →Hit-and-run entry: The mechanism through which contestability disciplines firms. If an incumbent earns supernormal profit in a contestable market, a firm enters, captures profit, then exits before the incumbent can retaliate. A powerful brand makes this strategy non-viable because entry requires sustained, costly brand investment before customers switch.
• →Market share as a proxy for market power: A firm's market share is not the same as contestability, but a very high share often reflects accumulated advantages — economies of scale, brand equity, exclusive contracts — that individually and collectively raise the cost of entry.
• →Supernormal profit and long-run equilibrium: In a perfectly contestable market, supernormal profit attracts entry and is competed away. Persistent supernormal profit alongside high market share is therefore evidence that contestability is limited, because the disciplining mechanism of potential entry is not functioning effectively.

This question tests students' understanding of contestability theory and how observable market characteristics — specifically market share and brand strength — serve as evidence about the height of barriers to entry, as set out in Edexcel spec point 3.4.7.a, which addresses the conditions required for market contestability and the factors that determine whether a market is effectively contestable in practice. Students are expected to move beyond simply defining contestability and instead apply the theoretical conditions — particularly the role of sunk costs and freedom of entry and exit — to real-world market structures in order to make a reasoned judgement.

Examined 4 times across Edexcel since 2017.

The tariff has risen sharply over time, with the concept progressing from a single-mark recall question in 2017 to a 25-mark evaluative essay in 2024, reflecting an increasing expectation of analytical depth and judgement.

• →Market Structures — understanding the spectrum from perfect competition to monopoly provides the structural context within which contestability arguments about market share and barriers to entry are applied.