Difficulty scores are the SEO market's answer to the patchwork state of all the data out there. All five tools we tested stood out because they do offer some version of a difficulty metric, or one holistic 1-100 score of how difficult it would be for your page to rank organically (without paying Google) on a particular keyword. Difficulty scores are inherently subjective, and each tool calculates it uniquely. In general, it incorporates PA, DA, and other factors, including search volume on the keyword, how heavily paid search ads are influencing the results, and how the strong the competition is in each spot on the current search results page.
Early versions of search algorithms relied on webmaster-provided information such as the keyword meta tag or index files in engines like ALIWEB. Meta tags provide a guide to each page's content. Using metadata to index pages was found to be less than reliable, however, because the webmaster's choice of keywords in the meta tag could potentially be an inaccurate representation of the site's actual content. Inaccurate, incomplete, and inconsistent data in meta tags could and did cause pages to rank for irrelevant searches.[10][dubious – discuss] Web content providers also manipulated some attributes within the HTML source of a page in an attempt to rank well in search engines.[11] By 1997, search engine designers recognized that webmasters were making efforts to rank well in their search engine, and that some webmasters were even manipulating their rankings in search results by stuffing pages with excessive or irrelevant keywords. Early search engines, such as Altavista and Infoseek, adjusted their algorithms to prevent webmasters from manipulating rankings.[12]
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