January 16, 2007

Of Course Ethics Books Are the Most Stolen Philosophy Books

Greg Dahlmann pointed me to Splintered Mind's Eric Schwitzgebel's post to the effect that ethics books are, well, you read the post title. But Eric has gone further, deeper, into the ethics book theft matter. He has numbers:
Missing books as a percentage of those off shelf were 8.7% for ethics, 6.9% for non-ethics, for an odds ratio of 1.25 to 1. However, I noted three concerns about these data that required further analysis. I've now done the further analysis.

Here are the concerns:

(1.) Older books are more likely to be missing, and the ethics books were on average a couple years older than the non-ethics books.

I addressed this concern by eliminating from the sample all books published prior to 1985. This brought the average age of the books to the same year (1992.9 for ethics, 1992.7 for non-ethics). On these reduced data, the ethics books were still more likely to be missing: 7.7% to 5.7%, for an odds ratio of 1.35 to 1 (p = .015).

(2.) Ethics books are more likely to be checked out than non-ethics books in philosophy, and there is a tendency for books that are more checked out to have a higher percentage of the off-shelf books missing -- not just a higher percentage of the holdings missing, but a higher ratio of missing to off-shelf-but-not-missing.

I addressed this concern by further reducing the sample, eliminating all the "popular" ethics and non-ethics books -- those cited at least 5 times in the relevant entries of the Stanford Encyclopedia of Philosophy. (This left only fairly obscure books, presumably known to and borrowed by only professors and advanced students in the field.) This actually seems to have increased the effect: 8.5% to 5.7%, for an odds ratio of 1.48 to 1 (p = .026).

(3.) Finally, some people were concerned that maybe law students were driving the effect. Therefore, finally, I eliminated from analysis all "law" books, defined as those books for which at least 10% of the U.S. holdings were in the four law libraries included in the analysis (UCLA, Harvard, Stanford, and Cornell law). This had little effect: 8.3% to 5.7%, odds ratio 1.46 to 1 (p = .044). Also, the percentage of ethics books missing from the four US law libraries was only 7.0%, versus 8.3% for the US non-law libraries.

So it's not (supposedly vicious) law students. And it's not a bunch of (supposedly conscience-impaired) undergraduates stealing Rawls. The effect is large, and statistically significant, just looking at books likely to be borrowed only by professional ethicists and students with a serious scholarly concern with ethics.

Based on these data, it seems indeed that ethicists do steal more books!


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