If America is serious about improving police behavior tomorrow, policy analysts need to know what police are doing today. We need the data, not just for some cities, but for all cities; not just for some years, but for all years. Republicans and Democrats should work together to impose a requirement that police agencies adopt a standard set of practices for recording data on the behavior of their officers and deposit that data regularly in a centralized public archive. These data should include the date, time, and location of police-citizen interactions, as well as enforcement outcomes and information on the use of force. The data should also be maintained indefinitely so analysts can measure changes over time. The scope of this effort is of a sufficient scale that it would likely require federal mandates and funding, but if better policing is the goal, open data is the first step.