In 1999, the congressionally requested Data Quality Study (the Study) found opportunities to improve ratemaking data quality. The U.S. Postal Service (USPS) agreed to make improvements, but concerns remained that it is still unclear, from an overall perspective, what actions USPS has taken to improve data quality. Ratemaking data quality has also factored into congressional deliberations to reform postal laws. Thus, questions remain about USPS's actions to improve ratemaking data quality and how proposed legislation will address long-standing issues in this area. GAO was asked to (1) describe key USPS actions that were responsive to the Study to improve the quality of ratemaking data and (2) discuss possible implications of postal reform legislation for ratemaking data quality. GAO did not assess the extent to which USPS's actions affected data quality. In its comments, USPS disagreed with GAO's finding on the need to reform the ratemaking structure. USPS also differed on GAO's finding that the legislation would likely lead to improving ratemaking data quality. It said "breakthrough improvements" would be unlikely without a significant increase in costs. GAO believes reform of the ratemaking structure is needed, but the outcome would depend on its implementation. Further, the legislative changes would likely lead to data quality improvements over time and at some cost.