Flaring of natural gas associated with U.S. unconventional tight oil production is a significant environmental and policy issue for the sector. We marshal granular data to identify the bottlenecks in the oil and gas value chain that physically cause upstream flaring at the well. Motivated by this descriptive analysis, we further analyze the economic reasons for flaring, market distortions that could exacerbate it, and the cost to society of flaring. We lay out an agenda for researchers and policymakers charged with understanding and regulating flaring.