Economic Definition of Lerner index. Defined.
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Term Lerner index Definition: The difference between price (p) and marginal cost (mc) as a fraction of price, that is [p-mc]/p. The Lerner index is usually taken as an indicator of market power because the larger the index, the larger the difference between price and marginal cost, that is, the larger the distance between the price and the competitive price. The Lerner index depends on the elasticity of demand. The Lerner index is also called the price-cost margin.