The cyclicality of R&D investment revisited
质疑Fabrizio和Tsolmon（2014）及Barlevy（2007）关于R&D投资顺周期性的结论，通过更合理的缺失值处理和模型扩展，确认了顺周期性但发现异质性更小，且外部融资比专利有效性更重要。
Summary In Fabrizio and Tsolmon ( Review of Economics and Statistics , 2014, 96 (4), 662–675) and Barlevy ( American Economic Review , 2007, 97 (4), 1131–1164) it was concluded that R&D investments are procyclical. Fabrizio and Tsolmon utilized a model based on Barlevy, but it differed in some respects and allowed for more heterogeneity. However, we doubt whether their implied trends are intended. Fabrizio and Tsolmon also set missing values for R&D equal to zero, leading to unrealistic jumps in investment and its first differences. We reconcile and replicate both the Fabrizio and Tsolmon and Barlevy papers by considering extensions that encompass both models. Furthermore, we treat missing values more appropriately and consider some alternative specifications to check the robustness of the results. Procyclicality is confirmed, but we find much less heterogeneity than Fabrizio and Tsolmon did. In particular, obsolescence and patent effectiveness are no longer important but external financing is.