Books featured in the BookBub email typically experience a significant spike in downloads, leading many titles to soar in their retailer rankings, perform better in recommendation algorithms, and sometimes even hit major bestseller lists like The New York Times or USA Today. The increased visibility driven by downloads from BookBub subscribers usually gives rise to additional downloads from readers who find the title through these other outlets. Extra sales beyond those generated by BookBub subscribers are what we call the “halo effect,” and this is one of the main measures of a promotion’s exposure level.
To find out more about this halo effect, we regularly ask our author partners to report their own results after each BookBub promotion. By combining this data with our own internal statistics, we’re able to calculate the number of downloads that do not come directly from BookBub subscribers, and therefore measure the broader exposure of our listings.
We’ve found that over the last six months, the average halo effect was around 60 percent for a discounted book, and over 80 percent for a free promotion. This means that, on average, a discounted title that sells 1,000 copies through BookBub links results in 1,600 sales overall, and a free promotion that generates 1,000 downloads through BookBub links results in 1,800 downloads overall.
*We are only able to directly track clicks for free books, so BookBub download numbers are estimates.
Because greater visibility fuels higher download totals, this effect multiplies. A book that performs particularly well with BookBub subscribers is more likely to gain above average traction elsewhere. For example, more BookBub downloads may lead to a higher retailer ranking, which in turn generates additional downloads. Furthermore, since free and steeply discounted promotions routinely drive the best subscriber response rates, those deals tend to be associated with higher halo effects in general.
It’s worth noting here that there are other possible causes aside from a pure halo effect that could lead to our partners reporting higher sales numbers than our internal data shows. Some BookBub subscribers may discover a title through our email but download the book through a different link, preventing us from tracking the sale, for example. Or, books may be promoted on platforms other than BookBub, which complicates halo effect measurement. And because our data was collected through voluntary surveys, there’s always a chance that the numbers are skewed or otherwise flawed, even though we were able to include a large sample size of past promotions.
However, these results demonstrate that a BookBub promotion generates significant traction beyond the response it receives from our own subscribers. And while this effect is particularly strong in the case of free promotions, any discount that gains visibility is likely to see at least some additional bump. As a result, paying to promote a limited-time deal can lead to many benefits beyond a surge in discounted sales, including the elevated levels of exposure that the halo effect helps measure.
*Please note that the averages we list on our pricing page only include activity we track directly; we do not take halo effect into consideration when calculating BookBub listing fees. This post has been updated on October 1, 2015 with the latest data.
Interested in partnering with BookBub on your next price promotion? You can submit your book for consideration here.
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