The Limitations of Industry Concentration Measures Constructed with Compustat Data: Implications for Finance Research
发现用Compustat数据（仅含上市公司）计算的行业集中度指标与基于全样本的美国普查指标相关性仅13%，且只有使用普查指标时才能验证理论预测，而Compustat指标可能误导产品市场研究结论。
Industry concentration measures calculated with Compustat data, which cover only the public firms in an industry, are poor proxies for actual industry concentration. These measures have correlations of only 13% with the corresponding U.S. Census measures, which are based on all public and private firms in an industry. Also, only when U.S. Census measures are used is there evidence consistent with theoretical predictions that more-concentrated industries, which should be more oligopolistic, are populated by larger and fewer firms with higher price-cost margins. Further, the significant relations of Compustat-based industry concentration measures with the dependent variables of several important prior studies are not obtained when U.S. Census measures are used. One of the reasons for this occurrence is that Compustat-based measures proxy for industry decline. Overall, our results indicate that product markets research that uses Compustat-based industry concentration measures may lead to incorrect conclusions. The Author 2008. Published by Oxford University Press on behalf of The Society for Financial Studies. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org., Oxford University Press.