Lerner's Index Lerner's index is an efficient way to measure the market power. Costs, revenue and price L=(P-MC)/P MC P-MC ATC DE AR MR MAX QuantityLerner’s Index Lerner’s index is an efficient way to measure the market power. L = (P - MC)/P 0 Quantity Costs, Revenue and Price D= AR MC MR QMAX E ATC P M C P-MC P