title: The use of free resources in a subscription-based digital library: a case study of the North Carolina AHEC Digital Library.
abstract: BACKGROUND
  The North Carolina (NC) Area Health Education Center's (AHEC) Digital Library (ADL) is a web portal designed to meet the information needs of health professionals across the state by pulling together a set of resources from numerous different sources and linking a pool of users to only the resources for which they have eligibility. Although the ADL was designed with the primary purpose of linking health care professionals to a set of licensed resources, the ADL also contains a significant number of links to free resources. These resources are available to any ADL member logging into their ADL account and to guest visitors to the ADL. While there are regular assessments of the subscription resources in the ADL as to utility and frequency of use, up until this point there has been no systematic analysis of the use of the overall set of free resources. It was decided to undertake an examination of the usage of ADL free resources over a 6-month period to analyze the utility of these resources to both ADL members and guests.
  
  
  METHODS
  Each time a resource is accessed through the ADL, it is logged in a table. This study used a SQL query to pull every free resource accessed between November 1, 2005 and April 30, 2006. An additional query also pulled the user information for each free resource accessed. Once the queries of the database were complete, the results were imported into an Excel spreadsheet and analyzed using basic descriptive statistics.
  
  
  RESULTS
  The vast majority of resource use through the ADL is to licensed resources. There are 2056 free resource URLs in the ADL, to which 1351 were linked out, meaning there was at least one link out to 65% of the free resources. The single most popular free resource was PubMed with 4803 link outs or nearly 20% of the total link outs to free resources. The breakdown of free resource use by different use groups indicates that the highest percentage of use of free resources was by guests followed by institutional affiliates and AHEC Faculty/Staff. The next 3 highest user groups accessing free resources are: paid members, preceptors, and residents.
  
  
  CONCLUSIONS
  The only free resource capturing a significant number of link outs is the free link to PubMed. This reflects the importance placed on traditional medical literature searching by the ADL clinical user base. Institutional affiliates access free resources through the ADL with the second highest frequency of all the user groups. Finally, in analyzing use of free resources, it is important to note the overall limitations of this survey. While link outs are excellent indicators of frequency of use they do not provide any information about the ultimate usefulness of the resource being accessed. Further studies would need to examine not only the quantitative use of resources, but also their qualitative importance to the user.
authors.affiliation: UNC Chapel Hill Health Sciences Library/CB # 7585, Chapel Hill, NC 27599, USA. mbschell@email.unc.edu
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Schell