Fred S. McChesney
We examine the problem of measuring market power when the firm has monopoly power in the output market and monopsony power in the input market - a case we refer to as 'dual-market' power. We show how the Lerner index, which measures the mark-up over the marginal cost, can be modified to reflect the firm's ability to set price above the competitive level.
Keith Hylton & Mark Lasser,
Measuring Market Power When the Firm Has Power in the Input and Output Markets,
Economic Inputs, Legal Outputs: The Role of Economists in Modern Antitrust
Available at: https://scholarship.law.bu.edu/faculty_scholarship/288