Figure 3

URL Availability by Year of Publication. 10, 208 URLs extracted from MEDLINE records from 1994 to 2006 were accessed once daily at random schedules for 30 days to determine link availability. The bar graph shows that URL availability seems to be time-dependent with those being published earlier showing a higher decay rate. The increasing number of URLs in MEDLINE abstracts by publication year (solid line) is also superimposed with the bar graph.