You want to know what gives librarians nightmares? 16 millimeter films.

There was a time when forward-thinking libraries the nation round built up impressive collections of such films. Suddenly: videos. I've worked in libraries where it took years to finally purge the final 16 mm metal casing, and make way for the new format.

The Douglas Public Library District now has quite a good collection of videos. We have tens of thousands of them. You see where I'm heading?

DVDs.

There are some interesting elements to this. On the one hand, just because a new format comes out, that doesn't necessarily mean the old one dies out immediately. For awhile, some technologies co-exist. That could be months. It could be decades. But how to know?

Even within a collection of videos, it seems to me that we have some differences. For instance, the demand for DVDs will probably center on new movies, feature films for adults. But is that as likely for children's videos? Or might we expect that many families have built up their own libraries of kid's films, and can be expected to keep at least one VCR in working condition for at least five years?

Or take the many videos we have in the "do it yourself" category. Or the PBS series videos. Do we need DVD or video? Both?

Here's another example: books on tape are now getting a serious run for the money by books on CD. Why? Here in Douglas County, we have an unusually high percentage of new cars. New cars come with CD players. If you've gotten into the habit of listening to books on your commute, you find it hard to give up.

So the library scrambles to work with the handful of vendors who are ready with books on CD, and are prepared to deal with the library's demand for discounts.

I'm tempted to say, "Thank God for the lasting endurance of one format: the printed book." But there's a big budgetary question even here. Say we get a new John Grisham book. It comes out first in hardback. We buy many copies. But it also comes out in paperback, and for many people, paperback is preferable. We buy many copies.

But we have a rapidly growing community of senior citizens. They find it easier to read large print books. We should buy many copies. That's three kinds of printed book.

Now we go back to that commuter. Not everybody springs for a new car. So we buy the audiotape. And we also need the CD.

We are now up to five versions of a single book. And if it comes out as a movie (and I imagine that with a Grisham book, it surely will), we have two more (video and DVD). Let's not even get into dueling e-book formats.

What's the net effect of all this multiplicity of formats? We buy fewer new titles. Instead, we duplicate whole collections.

There are good reasons for this: we want to track the use of the various formats, and what\'s popular in one, is usually popular in another. The public expects us to have things that they want, in the format they want.

Yet you can't help but see in this trend, the same trend afflicting our culture. While the packaging options are proliferating, the product count is going down. Why? Because the producers of content are merging. Instead of the 25 or so independent publishing houses extant a generation ago, we're down to three or four.

That's a story that would make a good movie. You won't be seeing it on 16 millimeter.