U.S. Postal Service: Actions Needed to Make Delivery Performance Information More Complete, Useful, and Transparent, GAO-15-756: Published: Sep 30, 2015. Publicly Released: Oct 5, 2015.

“U.S. Postal Service (USPS) measurement of on-time delivery performance has expanded greatly over the past 9 years, but remains incomplete because only 55 percent of market-dominant mail (primarily First-Class Mail, Standard Mail, Periodicals, and Package Services) is included (see fig.). The remaining 45 percent is excluded due to various limitations, such as not having barcodes to enable tracking. Incomplete measurement poses the risk that measures of on-time performance are not representative, since performance may differ for mail included in the measurement, from mail that is not. Complete performance information enables effective management, oversight, and accountability. In addition, the Postal Regulatory Commission (PRC) has not fully assessed why USPS data are not complete and representative. While PRC’s annual reports have provided data on the amount of mail included in measurement, they have not fully assessed why this measurement was incomplete or whether USPS actions will make it so. PRC may initiate a public inquiry docket (a type of proceeding) to improve data quality and completeness, but has not done so. Such a proceeding could facilitate evaluating data quality and identifying areas for improvement, as well as actions and time frames to complete improvements.”