The Program for the International Assessment of Adult Competencies (PIAAC) is a multicycle survey of adult skills and competencies sponsored by the Organization for Economic Cooperation and Development (OECD). The survey examines a range of basic skills in the information age and assesses these adult skills consistently across participating countries. PIAAC is the sixth of a series of adult skills surveys, sponsored by the National Center for Education Statistics (NCES), that have been implemented in the United States. This report describes the statistical methodology used to produce estimates of average scores and high, middle, and low proficiency levels of adult skills for every state and county in the United States.