The level of educational attainment in the United States is a central focus of public policy. The Obama administration, some states, large national foundations, and other organizations have set near-term goals to increase the number of Americans with college degrees. Achieving these goals is likely to involve a combination of increasing participation in higher education and growth in the percentage of those enrolling who succeed in earning post-secondary degrees and certificates. Both setting goals and assessing progress require clear and readily available data. The US Department of Education has increased the information available to students who are making decisions about college enrollment, but there is a growing consensus that the data available to assess the successes and failures of our postsecondary education system are inadequate. To remedy this problem, many policymakers and scholars advocate the creation of a national "unit-record" data system, which would follow students from their K-12 years through college and beyond. Such a resource would improve our understanding of how students with different characteristics fare, how well individual institutions and programs serve students in different circumstances, and how employment outcomes are related to postsecondary experiences. Reservations about compiling such a comprehensive data set rest primarily on privacy concerns. Perhaps even more important than more data is better understanding and use of the data we already have. A report issued in April 2015, based on a National Science Foundation-funded project at the George Washington University Graduate School of Education and Human Development, illustrates some of the misunderstandings that can arise when people use data about educational attainment without paying adequate attention to the sources of the data, the definitions of key terms or population groups, and what is actually being measured. This article shares some illustrative examples from the full report to highlight the types of misunderstandings, or seemingly conflicting answers to the same question, that can arise when attention to the key features of the data source is inadequate. All of the issues discussed here point to ways the selection of definitions, data sources, or time frames can modify the picture of educational attainment in the United States.