In 2007, the Northwest Evaluation Association (NWEA) and the Thomas B. Fordham Institute collaborated on "The Proficiency Illusion," a study that illustrated the issues created by having each state set its own standards for what constitutes student proficiency for reading and mathematics tests, while holding all states to the same accountability standards. By comparing the cut scores that determine proficiency for each state, the authors found that there was significant variation in the difficulty of proficiency levels among states. In some states, it is considerably easier for a student to pass their state test than it is for students in other states. In the four years since the study was published, the educational landscape has changed in many ways. Given all of the changes taking place in the field of education, and fortified with more recent data, the authors decided to update and enhance the original study so that it might inform the next generation of policies governing the nation's schools. The purpose of this study is to shine some light on the limitations of using proficiency rates based on inconsistent and arbitrary "passing scores" to make judgments about educational effectiveness. This report serves as a written summary of the authors' methodology and findings. Appended are: (1) Mathematics cut score estimates for 2009-2010; (2) Reading cut score estimates for 2009-2010; (3) Website References; (4) Sources for 2009-2010 state proficiency rates; (5) Deliberate changes to state cut scores; and (6) Full Methodology. (Contains 13 figures, 2 tables, 35 resources and 4 footnotes.)