[jsloa071]

Great question! We intended the article to be more of an introduction to the evaluation process for search algos and definitely glossed over the example's problem area here and should have talked more about the specific experiment we used as the example. We use TF-IDF in combination with the popularity scores for both algorithms mentioned. There are a few reasons we chose to experiment with the query-specific popularity - mainly, that global popularity wasn't as much of a signal for "helpfulness" for the user's intent as much as it was a signal for the most popular pages overall (i.e. turns out to be overview pages and most popular problems encountered on the platform), so it wasn't having the desired effect on ranking. We wanted to see whether using popularity within the context of the user's topic enhanced the utility of the popularity score. Plus, with Query-Specific ranking, when the user's keywords aren't an exact match with the document's language, we still receive a boost from users who previously scrolled further to find the match to solve their problem