Warning: this is a self-indulging post. (I can already hear the retort: "you mean all your others weren't...?")
Princeton University Press ran a small ad for my book last Sunday in the New York Times book review. I was curious if it would have any effect on sales, so I ran a little experiment. I checked the book's sales ranking in amazon.com at periodic intervals starting on Saturday afternoon. I also took down the corresponding information from three amazon sites abroad: amazon.co.uk, amazon.de, and amazon.fr. The idea was that an ad in the NYT book review should not affect sales in Britain, Germany, or France, as the NYT (especially its Sunday supplements) is not easily available in those markets. The comparison also allows me to control for day-of-week effects: "serious" books may experience higher sales during weekdays than on the weekend. In other words, the research design was a simple diff-in-diff.
Here is where things stood, as of this morning:
(Note a couple of things about the chart: I use the log scale for the vertical axis, and a higher number means poorer sales.)
So what did I learn (except for the generally abysmal ranking of the book: the average rank over all four markets is around 20,000 among all English-language books...)?
First, I was surprised that there was not a more perceptible impact on U.S. sales. The sales rank at amazon.com dropped from around 15,000 on Sunday midday to around 7,000 this morning. I suppose I exaggerated how many people read the NYT. (Harvey Mansfield once defined a liberal as someone who wouldn't have anything to do if the NYT did not come out on Sundays. I guess there are fewer liberals than I thought.) Now, as it turns out, amazon.com ran out of the book midway during the experiment. Can I comfort myself (and my publisher) by thinking that this had something to do with the result?
Second, I was puzzled by the unexplained and very steep rise of the book in the German site. On amazon.de the book went from a sales rank of around 27,000 on Saturday evening to a rank below 1,000 this morning. I have no idea what may have caused this. I doubt it was the ad in the book review. So I am clueless.
Third, why is the sales rank in France so stable compared to the three other countries? What makes the French so consistent in their purchases of English-language books over time?
Bottom line: I was expecting to get some easy results, instead I ended up with lots of questions.