Gartzke and Li (2003b) formulate a mathematical relationship between “trade share,” “trade dependence,” and “trade openness,” and use this to argue that the disparity between the findings in studies by Barbieri and those of Oneal and Russett and others can partly be explained by features of variable construction. This article argues that although Gartzke and Li's formulation is very useful, the authors draw some conclusions from their analysis that only hold under very restrictive assumptions. “Trade share” does not in general measure a state's disconnectedness from the world trading system, and “trade share” is not associated with a high risk of interstate dispute if “trade dependence” is associated with a low risk. What Gartzke and Li attribute to “trade share” is rather an effect of trade substition from one partner to another. Finally, the trade openness variable may be a proxy for country size. The discussion also illustrates some problems involved in controlling for variables that are related by definition to a key explanatory variable.