On June 16, 2009, the Congressional Budget Office (CBO) outlined the potential impact of health reform on the federal budget.  In a letter to the Senate Budget Committee, the CBO warns that "without meaningful reforms, the substantial costs of many current proposals to expand federal subsidies for health insurance would be much more likely to worsen the long-run budget outlook than to improve it."   Moreover, despite consensus about the need to make changes to make the health sector more efficient, such as paying providers for value, providing incentives for both providers and patients to control costs, and promoting comparative effectiveness information, "little reliable evidence exists about exactly how to implement those types of changes—especially at the level of specificity required for legislation."