We then build upon this review by showing that these three approaches can be combined into a "multilevel" research and assessment program. Each level has offsetting strengths and weaknesses; thus, combining them can promote the broadly based, systematic study and documentation of library value. We conclude by integrating all three approaches into a coordinated framework for academic library value assessment. The Structure of the Academic Library Value Literature By definition, library value studies typically seek to show that library usage or library programs provide benefits to users or contribute to key goals of the library's parent institutions. Most commonly, these impacts include promoting user information literacy, advancing student learning in subject fields, and increasing student graduation and retention rates. Other studies, typically conducted at large research universities, have focused on impacts like supporting faculty research and contributing to institutional imperatives like the securing of grants. The resulting body of scholarship is large and diverse, and it has produced a great deal of knowledge about library value. However, little attempt has been made to outline or distinguish between various approaches and methods or to consider this body of work as a whole. Literature reviews in most library value studies cite a small selection of previous work without taking a broader perspective, and even the Value of Academic Libraries report does not offer a means to fully conceptualize and analyze the literature in this field. Accordingly, it would be useful to have a general conceptual framework for library value studies. Such a framework could help to reduce the seeming complexity of this literature and more clearly reveal the elements (in other words, categories) within it. Categorization is key; it plays a central role in human cognition, serving to organize and simplify the world and various kinds of phenomena within it. 2 The benefits of effective categorization are quite familiar to librarians-library collections could not be readily organized or understood without the Dewey and Library of Congress classification systems. Levels of analysis represents an obvious choice for a categorization scheme. This concept, well established in several social sciences, posits that most social phenomena can be analyzed at multiple levels, ranging from smaller to larger units of aggregation. 3 For example, psychologists might view individual behavior as resulting from individual factors like a person's motivations or emotions. This seems obvious and natural, but it is not the only level that can be employed. Behavior can also be influenced by lowerlevel biological factors, such as chemical influences on the brain. In other words, an individual's actions can be explained through the effects of his or her constituent parts. Alternatively, individual behaviors can be shaped by factors at a higher level of aggregation (for example, by the dynamics of membership in a larger group). Research at all of these analytic...