In 2015, Kadaxis (with some help from Bowker, Firebrand and OnixSuite) set out to investigate whether publishers were adding keywords to book metadata. The conclusion was that of the 150,000 publishers reviewed, most weren't adding keywords, and of those publishers who did, the volume and quality of keywords was low.
Anecdotally, we've seen a significant shift in the past three years in the priority publishers give to keywords. We wanted to understand this change more deeply, but instead of taking a large sample of publishers, we adopted a qualitative approach and narrowed our analysis to 846 fiction titles with significant sales. By looking at how keywords are used on a publisher's most important titles, we can infer how important keywords are to a publisher and gain some insight into different keyword methodologies.
Keywords matter to the top publishers: of the 846 books we analyzed, 69% had keywords - a significant increase to three years ago.
Most publishers still target a 500 keyword character count. Of the books with keywords, 44% had a character count between 480 and 500 characters. See our investigation into why 500 keyword characters is not optimal for selling more books on Amazon:
Optimization savvy publishers are emerging though: 6.2% of books had keyword character counts above 500, while 2% had character counts above 1000 characters (many of these are Kadaxis clients).
Almost all of the top fifty most commonly used keywords across all books in our set related to category names.
The keywords "fiction" (most common) and "fiction books" (6th most common) were seen throughout the sample set. Search engines are able to derive whether a book is fiction or not by examining the book’s categories, so adding these terms as keywords is often not necessary. Likewise, BISAC and browse node (Amazon only) category names are also indexed by search engines, so if a book is assigned to a category, repeating the category name as a keyword won’t increase the book’s visibility in search. Category and genre names are relevant and appear to make sense as keywords, but understanding how search engines index metadata can often mean a more efficient use of the keyword field.
One observation we've made from working with publishers, is that Amazon applies rules discriminately. Large accounts are generally afforded more relief from the rules, and it appears many publishers may be aware of this extra freedom. (See section "Keywords to avoid" from Amazon's rules for KDP authors).
Of our sample set with keywords, 4% of books included the term "bestseller", while 15% broke the "Subjective claim about quality" rule by stating that their books were the “best”, for example: “best horror books”, “best selling fiction author”, “best american novel” and “best fantasy series”.
We also found countless examples of keywords comprised of competitive author and title names, along with the the use of Amazon program names (e.g. "kindle" as a keyword). One publisher even tried to cash in on deal days with the keywords: “cyber monday deals” and “black friday deals”.
Amazon likely filters out prohibited terms, but one exception is the use of competitive title and author names which, when indexed, do improve search visibility.
Publishers with high sales volumes take keywords seriously and in most cases add keywords to their book's metadata. The quality and volume of keywords has improved significantly over the past three years as we've seen publishers move from rarely adding keywords to commonly adding keywords. While keywords were generally well considered, when assessing phrasing, term redundancy, volume and other characteristics used to assess keyword efficacy on Amazon, the trend highlights coverage as a priority for most publishers, ahead of the more involved specifics of optimization. The industry is evolving though, and gaining a more sophisticated understanding of how search works. Our prediction is that in our next review we’ll see an even greater incidence of highly optimized keywords, incorporating this growing body of knowledge.