The study looked at over 550,000 articles, which contained over 2.2 million links to external websites. It found that 72 percent of those links were “deep,” or pointing to a specific page rather than a general website. Predictably, it found that, as time went on, links were more likely to be dead: 6 percent of links in 2018 articles were inaccessible, while a whopping 72 percent of links from 1998 were dead.