Book excerpt: Drawing on studies funded by the Lumina Foundation, the nation's largest private foundation focused solely on increasing Americans' success in higher education, the authors revise current theories of college student departure, including Tinto's, making the important distinction between residential and commuter colleges and universities, and thereby taking into account the role of the external environment and the characteristics of social communities in student departure and retention. A unique feature of the authors' approach is that they also consider the role that the various characteristics of different states play in degree completion and first-year persistence. First-year college student retention and degree completion is a multi-layered, multi-dimensional problem, and the book's recommendations for state- and institutional-level policy and practice will help policy-makers and planners at all levels as well as anyone concerned with institutional retention rates—and helping students reach their maximum potential for success—understand the complexities of the issue and develop policies and initiatives to increase student persistence.