15 March 2006
I think it's fair to say that index entries that no one looks up are, well, better left out of the index in the first place. If you're reading a book about the cardiovascular system, there's little point in including the index entry "jack-o-lanterns."
It's at this point that I've love to say, "Enough said," but I'd be wrong. That's because having entries that no one looks up isn't really a problem, as long as you don't have too many of them. Ignoring the costs of the physical space they require, or the indexers' and editors' resources in making them actually appear in that physical space, unused index entries can exist without anyone really caring, like pennies in a penny jar. As long as the jar isn't full, no one cares.
Why was the entry there in the first place, though? There are some legitimate reasons, of course, with the most legitimate being a reflection of an author's non sequitur. It's not too far-fetched to imagine a cardiovascular surgeon authoring a textbook about the cardiovascular system, taking a moment to wax poetic in a footnote about how the surgically cutting into the chambers of the human heart always remind him pumpkin carving on Halloween. If he takes even a half-sentence to explain why heart surgery has something in common with ritualistic gourd mutilation, the indexer will notice this and create that silly entry for "jack-o-lanterns." No one will look it up, but that's not the indexer's fault, is it? She's just doing her thorough-as-usual job.
Then there are the indexers who include things without realizing who the audience is. They include ideas that are too esoteric, off-topic, general, or inappropriate for people to look up. For example, in a book about pet care, they might include an entry for "schnausers. See dogs." Alternatively, they index the ideas people will look up, but under labels that no one would look up, like using the term "octothorpe" as a name for the # symbol.
And of course there are always the honest mistakes: spelling or typographical errors, document file anomalies, outdated indexes for new materials, and so on.
What most indexers seem to forget, however, is that just as these odd index entries might be created by accident -- author silliness, indexer ignorance, production oversight -- those very same index entries might be discovered by accident, too: reader serendipity. One of the great advantages of printed indexes over search results (or search-accessed indexes) is the serendipity that results from browsing. Just as we're likely to discover interesting words in the dictionary while trying to look up something else -- look up "Jefferson, Thomas" and find yourself reading about jeffing and jeffus -- so we might discover interesting things those indexes.
If you found "jack-o-lanterns" in a cardiology textbook, wouldn't you follow the entry? I know I would. And that's why there's one last reason for including these unlikely-to-be-used entries in indexes: sheer joy.
Did someone say, "bikini emergency"?