MATLAB Replication Code for “Reassessing Market Power Indices: When Concentration and Markups Fail to Predict Efficiency”
Description
This repository contains MATLAB replication code and generated outputs for the simulation-based results in the paper “Reassessing Market Power Indices: When Concentration and Markups Fail to Predict Efficiency”. The paper examines whether the Herfindahl index and the market-share-weighted Lerner index correctly rank Cournot markets by normalized total-surplus efficiency. The analysis considers homogeneous-good oligopoly environments with linear inverse demand and either constant or increasing marginal costs. The deposited materials reproduce: (1) the benchmark fixed-n pairwise directional-accuracy results reported for n=1,2,3,4; (2) the subgroup correlation diagnostics for the asymmetric constant-marginal-cost duopoly reported in Appendix C.2; (3) the expanded-support diagnostics for symmetric increasing marginal costs reported in Appendix C.3; and (4) the subgroup pairwise-accuracy and correlation diagnostics for the asymmetric increasing-marginal-cost duopoly reported in Appendix C.4. No external or proprietary empirical data are used. All market observations are generated computationally from the parameter distributions documented in the manuscript and MATLAB scripts. The programs use fixed random-number seeds and report parameter supports, feasibility rates, numerical tolerances, subgroup cut points, pairwise-ranking outcomes, tie frequencies, Monte Carlo standard errors and numerical validation checks where applicable. Generated results are provided in CSV, MAT, and PDF formats.