How reliable are those URLs in your OPAC? The Chesapeake Project Legal Information Archive which harvests and preserves relevant digital information from the web, has been producing reports on "link rot" for several years. They define link rot as "a URL that no longer provides direct access to files matching the content originally harvested from the URL and currently preserved in the Chesapeake Project's digital archive."

Their new report is now available:

• Breaking Down Link Rot: The Chesapeake Project Legal Information Archive's Examination of URL Stability, By Sarah Rhodes, LLRX (March 1, 2011).

This study is particularly relevant to government information specialists because more than 90% of their sample URLs were from state governments (state.[state code].us), organizations (.org), and government (.gov) the top-level domains.

Their data show that link rot frequency for .gov files was 10% in 2008, 13% in 2009, and 25% in 2010. State-level URL link rot was even worse: 10.8% in 2008, 15.8% in 2009, and 32.1% in 2010.

The authors qualify their findings, noting that the study is "not meant to be broadly applicable or to provide a representation of link rot throughout the universe of web resources" but only reports on those items in the Chesapeake Project archive. It also says, however, that the study provides "insight into the vulnerability of law- and policy-related web resources selected by experienced law librarians from seemingly stable open-access web sites hosted by reputable organizations and state and federal governments."

Significantly, "none of the content analyzed in this study has been truly lost; all of the content has been preserved in a digital archive" at The Chesapeake project.