Over the past two decades market forces have been increasingly used as a mechanism to drive improvements in quality and efficiency in health services. Information fuels markets, and the publication of comparative data has been, and will remain, a high profile feature of health policies of all UK political parties.1 2 3 The Department of Health in England, regulators such as the Care Quality Commission,4 professional organisations such as the Society for Cardiothoracic Surgery,5 Dr Foster Intelligence from the private sector,6 and the health service through NHS Choices7 have all contributed to the plethora of information that is now available to whoever wants to look at it.

Who are the potential audiences? Clinicians and managers clearly require information about how well they are doing to improve their work. Policy makers also need to make judgments, and the public, usually through the media, may want to use this information to hold those in the health service to account. But the spotlight is increasingly on patients—the people who use the service—to drive change. Market advocates believe that patients want to be able to choose between different providers; that given good information they will do so; and that these choices will be a major force driving improvement in services.8 They cite evidence,9 sometimes selectively, supporting their views. We use research evidence to challenge these expectations, explain why we think patient choice is not at present a strong lever for change, and suggest ways in which currently available information can be improved to optimise …