International R&D spillovers: A comment
重新审视Coe和Helpman关于技术通过贸易渠道跨国溢出的计量模型，指出其加权方案存在“加总偏误”，提出替代方案并修正“索引偏误”，发现一国贸易开放度越高，越可能受益于外国研发。
Coe and Helpman presented evidence consistent with the hypothesis that technology spills over across countries through the channel of trade flows, and provided estimates of the magnitude of these spillovers. We re-examine two features of their econometric model. First, we argue that the weighting scheme they used to compute foreign R&D capital stocks is subject to an `aggregation bias'. We suggest an alternative weighting scheme that is theoretically much less biased and that yields somewhat better empirical results. Second, we correct an `indexation bias' and generalise their empirical framework by analysing how the output elasticity of foreign R&D depends on a country's openness to trade. The empirical results confirm that the more open to trade a country is, the more likely it is to benefit from foreign R&D.