Chapter 3 describes how high quality and representative data was collected from traders, with an emphasis on sampling and survey strategies that could apply broadly to surveys of informal populations.It describes a trader census of tens of thousands of shops, how traders were sampled from this census, and strategies to reduce the likelihood that – for example – an enumerator avoids a shop where a trader is busy and picks the shop without customers. Next the chapter introduces strategies to increase trust with skeptical respondents, and strategies to enforce sampling and survey protocols. Last, the chapter discusses the brute-force approach to defining market association membership, and discusses implications for future researchers who aim to identify associational membership in a population.