Governments can act to make markets work better for the poor. The first step is to identify the size and nature of the problem. Our proposal focuses on using largely unexploited, micro-level price data, to provide policymakers with near real time capacity to assess how well markets are working for the poor. Our proposal is to combine spatially detailed and disaggregated price data with publicly available satellite lights data to geographically pinpoint markets serving poorer regions. This combined data can be used to track trends and conditions in markets and can alert policymakers of changes that may negatively affect the poor.