Demand-driven acquisitions (DDA) programs have become a wellestablished approach toward integrating user involvement in the process of building academic library collections. However, these programs are in a constant state of evolution. A recent iteration in this evolution of ebook availability is the advent of large ebook collections whose contents libraries can lease, but not own only if they choose to do so. This study includes an investigation of patron usage and librarian ebook selection by comparing call number data generated by usage of three entities: (1) an ebrary PDA; (2) Academic Complete, which is a leased collection of ebooks; and (3) subject librarian selections based on the YPB approval plan at Iowa State University. The context is provided through a description of the development and evolution of demand driven acquisitions programs with an analysis of where libraries have been and where they are going with enhancing the collection development in academic libraries.wenty-five years ago, Futas and Vidor raised the question of what "constitutes a good collection."1 Although more than two decades have passed, creating a collection that effectively meets the needs of its patrons remains a core challenge for any library, academic or public. Since the days of Callimachus and the Alexandrian Library, librarians have often struggled to build collections for not only their contemporaries, but also for those individuals who will explore the collection's contents in decades or centuries to come.2 Over the years, diligent collection development librarians endeavored to create a balance between the exhaustiveness suggested by the seventeenth-century French bibliographer Gabriel Naudé, who observed that there was not a book "whatsoever, be it never so bad or disparaged, but may in time be sought for by someone," and the more modern belief of Yale librarian Andrew Keogh, who averred that the "number of volumes in a library means little more than their cubage or their weight; it is appropriateness, it is quality, that counts."
3To assist with the daunting task of keeping pace with the deluge of publishing that accelerated during the years following the Second World War, librarians sought to manage the selection process through the newly invented approval plan approach. The