According to a 2014 study conducted at Harvard Law School,
more than 70% of the URLs within the Harvard Law Review and other journals, and 50% of the URLs within United States Supreme Court opinions, do not link to the originally cited information.
The New Yorker piece where I read those statistics describes a website called Perma.cc that allows you to create a permanent link to a URL you cite in your brief so that anyone later reading your brief (or a court decision citing that URL) will be brought to the permanently archived version of the link rather than to a URL that may no longer exist.
My own 2004 Fordham Law Review note discussed how ticket scalping laws failed to account for event promoters’ wholesale adoption of business practices previously reserved for scalpers. I researched contemporaneous news reports of concert venues and sports teams holding back tickets from public on-sale releases, then selling those tickets at massive markups – behavior that New York State deemed illegal if scalpers did it.
When I checked the 24 unique URLs in my note, only six still functioned properly. Links to the websites of Harvard Law School, the Official Nobel Prize Committee, and the New York State Attorney General were among the broken ones. In many cases, links to news articles were redirected to a site’s front page, while others generated “404 Page Not Found” errors. In any event, 75 percent of my note’s links are now useless.
Not long after my note’s publication, New York State amended its scalping law in ways I suggested (n.b. correlation is not causation). Although the prior statute is available online, much of my note’s source material is not.
I agree wholeheartedly with the New Yorker:
Perma.cc has already been adopted by law reviews and state courts; it’s only a matter of time before it’s universally adopted as the standard in legal, scientific, and scholarly citation.