Do CDs have a life expectancy of 10 years?
In 1994 I read an article in the British music journal The Wire that claimed that compact discs have a life expectancy of ten years. I have seen references to an article in Scientific American making the same claim and heard that this has been confirmed many times by other studies. The only thing is, uh, I've had a few CDs for more than ten years, and they play fine. So what exactly is the deal? Does the speed of degradation have to do with how often the CD is played? I mean, most of the time, my CDs are sitting in their cases on my shelf. Please tell me whether I should be getting my Sonny Rollins fix from some other recording technology (like, say, vinyl).
I got a lot of letters along these lines in the late 1980s and didn't dismiss the idea of "CD rot" out of hand. But I suspected that predictions of imminent CD meltdown were exaggerated — and time has shown they were. Physical survival of recordings is only part of the story, though. The real threat is loss of the technology needed to play them back. Most people think they'll be able to enjoy their CDs for a lifetime, and maybe they will. But good luck playing your eight-track tapes.
This point is well made in the Scientific American article you mentioned, an updated version of which can be found at www.clir.org/pubs/archives/ensuring.pdf. Author Jeff Rothenberg of the Rand Corporation includes a photograph showing a replica of the Rosetta stone along with various digital media from the past 50 years, including punch cards, punched paper tape, 5.25-inch and 8-inch floppy disks (remember 8-inch floppy disks, gramps?), and a large multiplatter disk from an old mainframe. The Rosetta stone is still readable after 2,200 years, but the digital media are not — not because the media have deteriorated, but because the machines needed to play them back have for practical purposes disappeared.
Rothenberg was writing about information technology, but his argument applies to entertainment media too. Take those vinyl records you mention. I've got boxes of them in the attic, right next to my old turntable. I haven't played a record in ten years. The little researchers have never seen one. I may drag one out to show them, as I might show them what a rotary-dial telephone and a typewriter look like, but unless they get into antiquities they'll never own one. Vinyl technology isn't gone, but it's surely slipping away, and with it anything recorded in that medium that never made the transition to CD.
But let's get back to your question. You figure CD players will last your lifetime (although technology offering "better than CD audio" is already available and may not be backward compatible forever). You're more worried about the disks. The longevity of CDs and other optical storage media is controversial. CD manufacturers generally claim their products will last 100 years and possibly much longer, based on "accelerated aging" tests. (Typically these involve subjecting the media to heat.) Skeptics say five to ten years is more like it, but that seems alarmist where nonrewritable CDs are concerned. The "CD rot" stories that circulated years ago apparently sprang from substandard disks sold by a CD bootlegger in Italy, in which the aluminum oxidized after a short time. That won't or at least shouldn't happen with a properly made CD, nor will such a disk wear out with repeated use (although scratches and other abuse may cause it to fail).
Then again, Rothenberg says 5 to 59 years, which gives you an idea of the uncertainty here. Rewritable CDs are more uncertain still. Common wisdom is that CD-Rs will last 70 to 100 years or more, CD-RWs perhaps 30 years. But the technology is much newer. Even a casual glance at the literature suggests that extraordinary precision is required and that the different dyes used have different longevity and playback characteristics. Already I find that CD-RWs won't work in all CD players, and you have to wonder what will happen a decade or two down the road.
The truth is, nobody knows. "There is considerable disagreement among experts about how long a given medium can be expected to last, and experience seems to imply that the answers can be quite different depending on storage conditions, etc. Furthermore, different batches of media from different manufacturers can apparently have rather different lifetimes, so narrowing these estimates is difficult," Rothenberg tells me.
Consider a storage medium considered cutting edge 50 years ago — magnetic tape. It's now recognized that tape degrades after 20 years, maybe sooner, unless you're extremely careful. Some tapes used for the 1960 U.S. census became unreadable and the data was almost lost. (Luckily they had a backup on microfilm, which supposedly will last 500 years, although even microfilm has doubters.) For all our modern advances, by far the most durable storage technology ever devised remains the written word, as recorded in stone, papyrus, and clay.