This introductory essay for the journal Symposium presents an overview of issues related to ‘Q-Squared in Policy: the use of qualitative and quantitative methods of poverty analysis in decision-making’. We focus on issues raised on the supply side of data use, relating, inter alia to the informational content and policy usefulness of different types of data and analysis. These issues are grouped under the headings of: outcomes vs. processes, unpacking processes and thick and thin. We begin however, with a brief discussion of one aspect of the demand side, namely the politics of data use, given its centrality to the issues at hand.