The life and death of URLs in five biomedical informatics journals.

OBJECTIVE: To determine the decay rate of Uniform Record Locators (URLs) in the reference section of biomedical informatics journals.

METHODS: URL references were collected from printed journal articles of the first and middle issues of 1999-2004 and electronically available in-press articles in January 2005. We limited this set to five biomedical informatics journals: Artificial Intelligence in Medicine, International Journal of Medical Informatics, Journal of the American Medical Informatics Association: JAMIA, Methods of Information in Medicine, and Journal of Biomedical Informatics. During a 1-month period, URL access attempts were performed eight times a day at regular intervals.

RESULTS: Of the 19,108 references extracted from 606 printed and 86 in-press articles, 1112 (5.8%) references contained a URL. Of the 1049 unique URLs, 726 (69.2%) were alive, 230 (21.9%) were dead, and 93 (8.9%) were comatose. URLs from in-press articles included 212 URLs, of which 169 (79.7%) were alive, 21 (9.9%) were dead, and 22 (10.4%) were comatose. The average annual decay, or link rot, rate was 5.4%.

CONCLUSION: The URL decay rate in biomedical informatics journals is high. A commonly accepted strategy for the permanent archival of digital information referenced in scholarly publications is urgently needed.