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 this time 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.
500 characters was a target for many publishers. Of the books with keywords added, 44% had a keyword character count between 480 and 500 characters. See our investigation into why 500 keyword characters is not optimal for selling more books on Amazon:
Keyword savvy publishers are emerging though: 6.2% of books had keyword character counts above 500, while 2% of books with keywords had character counts above 1000 characters (most of these were Kadaxis clients).
Almost all of the top fifty most commonly used keywords across books related to category names.
The keywords "fiction" (most common) and "fiction books" (6th most common) were seen throughout our sample set. Search engines can derive whether a book is fiction or not by examining the book’s categories, so adding these as keywords is often redundant. Likewise, BISAC and browse node (Amazon only) category names are also indexed by search engines so if a book is assigned to a category, it's generally not necessary to repeat the category name as a keyword. While category names are relevant as keywords and appear appropriate, in most cases they don’t add to a book's visibility on Amazon search.
One observation we've made from working with so many publishers, is that Amazon applies rules discriminately. Large accounts are generally afforded more relief from the rules, and it appears that many publishers are 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”, “best fantasy series”.
In addition, we found countless examples of keywords comprised of competitive author and title names, along with the the use of Amazon program names (such as using "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 many prohibited terms which means their inclusion won’t improve search visibility. One exception to this case is the use of competitive title and author names which, when allowed, are indexed and can improve search visibility.
Publishers with high sales volumes take keywords seriously and in most cases do add keyword 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 frequently adding keywords (even if the target count is based on the outdated assumption that 500 characters is optimal). However, while keywords are often well thought out and appear appropriate to a human observer, in most cases keywords aren’t created with Amazon search optimization in mind. This is evidenced by analyzing keyword phrasing, term redundancy, volume and other characteristics used to assess keyword efficacy on Amazon. The positive news though, is that the industry is evolving and gaining a more sophisticated understanding of how search works. Our prediction is that in our next review we’ll see an even higher incidence of search optimized keywords that incorporates this growing body of knowledge.