The tape formats are listed with Obsolescence Ratings as follows:
Extinct: Only one or two playback machines may exist at specialist laboratories. The tape itself is more than 20 years old.
Critically endangered: There is a small population of aging playback machinery, with no or little engineering or manufacturing support. Anecdotal evidence indicates that there are fewer working machine-hours than total population of tapes. Tapes may range in age from 40 years to 10 years.
Endangered: The machine population may be robust, but the manufacture of the machinery has stopped. Manufacturing support for the machines and the tapes becomes unavailable. The tapes are often less expensive, and more vulnerable to deterioration.
Threatened: The playback machines are available; however, either the tape format itself is unstable or has less integrity than other available formats, or it is known that a more popular or updated format will be replacing this one in a short period of time.
Vulnerable: This is a current but highly proprietary format.
Lower risk: This format will be in use over the next five years (1998-2002).
These ratings are subjective and are based primarily on sampling done within the United States. The viability of the various formats may differ from one region to another.
Format obsolescence is a serious concern for videotape collections. By the early 1980s, the first 2" Quad format was no longer supported or produced. More recently, the 3/4" U-matic tapes that were popular throughout the 1970s and 1980s have also joined the ranks of unsupported technology. This document does not address the equally serious format obsolescence and preservation issues associated with audio tapes.
In addition, recent studies by the National Media Laboratory indicate that magnetic media has a life expectancy of approximately 10 to 30 years. Based on this estimate, many collections of videotapes must undergo immediate preservation recopying. Many other videotape collections are past their estimated life expectancy. Furthermore, many playback machines are obsolete. There are few places dedicated to maintaining the machinery required to recover information from old, compromised videotapes.