Market power

Market power is the ability of a firm or other market participant to influence prices or other trading conditions rather than simply accept them.

Price elasticity of demand: Price elasticity of demand measures how much quantity demanded changes when a product’s price changes. Demand elasticity determines how much a seller can raise price before losing customers.
Antitrust: Antitrust is the body of laws and policies intended to protect competition and restrain harmful market conduct. Antitrust authorities use market power to assess whether conduct or mergers may harm competition.
Perfect competition: Perfect competition is an idealized market structure with many firms, homogeneous products, and free entry and exit. Firms in this benchmark accept the market price rather than influence it.
Relevant market: A relevant market is the set of products and geographic areas used to analyze competitive constraints. Market power cannot be assessed without specifying which alternatives meaningfully constrain a firm.
Deadweight loss: Deadweight loss is the loss of total surplus when mutually beneficial trades do not occur. Prices above competitive levels can reduce output and prevent beneficial transactions.
Marginal revenue: Marginal revenue is the change in total revenue from selling one additional unit. A firm with market power faces marginal revenue below its price when demand slopes downward.
Merger control: Merger control is the review of proposed mergers and acquisitions by competition authorities. A merger may create or strengthen market power by reducing competitive constraints.
Monopoly: A monopoly is a market supplied by a single seller without close substitutes. Monopoly is the limiting case of seller market power, though real monopolies may still face constraints.
Market concentration: Market concentration describes how market activity is distributed among firms. Concentration can signal conditions favorable to market power, but does not establish it by itself.
Consumer surplus: Consumer surplus is the difference between what buyers are willing to pay and what they actually pay. Market power can transfer surplus from buyers to sellers through higher prices.

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