‘Market’ and ‘market economy’ exercise a powerful, even magnetic grip on our collective imagination. But what do we mean by ‘market economy’? Does it make sense to speak of a ‘nonmarket economy’, and if so, what does it mean? How are the ideas of ‘market economy’ and ‘nonmarket economy’ related? Focusing on EC anti-dumping law, this article seeks to answer these questions. It argues that the legal concept of ‘nonmarket economy’ in EC anti-dumping law has been socially constructed, by means of relations among a plurality of institutional and normative sites, as part of a changing configuration of legal ideas in specific historical circumstances, and in contexts of political, economic, social, and symbolic power. This argument is articulated in three parts. First, the concept of ‘nonmarket economy’ in EC anti-dumping law, though drawing on earlier elements, had its main roots in the early Cold War. Second, starting in the 1960s, the GATT multilateral negotiating rounds began to define more specific international rules of the game, but a variety of more localised processes played essential roles as forces of change. Of special importance were, first, the tension between legislative rules and administrative discretion in the United States, and, second, the Europeanisation of foreign trade law in the course of European integration. Third, the EC law concept of ‘nonmarket economy’ was born in the late 1970s. The main reasons were changes in the international anti-dumping law repertoire, specific ideas in Europe about comparative economic systems, and the perceived emergence of new economic threats, including exports from China.