What Does Trade Openness Measure?
研究了贸易开放度（总贸易与GDP之比）这一常用指标的信息含量，发现其跨国差异更多来自GDP波动而非贸易，且反映的是经济距离和部门生产分布特征。
Abstract An empirical measure of trade openness is defined as the ratio of total trade to GDP, and represents a convenient variable routinely used for cross‐country studies on a variety of issues. However, the effects that the crude measure captures remain ambiguous, making it difficult to interpret the empirical results. Drawing on several strands of the literature, this study examines the informational content of the trade openness measure using intranational and international data. We find that, even for fully integrated economies within a country, trade openness is approximately half as variable as it is for segmented diverse countries around the world. The information it conveys is better characterized as the extent of the economic remoteness and idiosyncratic distribution of sectoral production. The cross‐country variation of trade openness derives more from the variability in GDP than trade.