Gaining Comparative Advantage Through Discretionary Expenditures: The Returns to R&D and Advertising
研究研发和广告支出能否为企业带来比较优势从而获得超额利润，在控制企业特定因素和支出与利润的反馈后，发现其会计和股票市场回报远低于以往研究，且隔离机制不足以产生长期比较优势。
We explore the extent to which R&D and advertising expenditures generate a comparative advantage that allows firms to earn supranormal profits. After controlling for unobserved firm-specific factors and the feedback between discretionary expenditures and profitability, our results suggest substantially lower accounting and stock market returns to R&D and advertising than indicated in previous research. Isolating mechanisms, which prevent imitation, do not appear sufficient for either R&D or advertising expenditures to generate, on the average, a long-run comparative advantage.