No other search criteria, just yoursite.com? Hm. Largest proportion of non-text, or of worthless text? That wasn't aimed at you: I just tried my own sitename. #1 was the index page-- which nobody ever goes to except when they're randomly exploring after landing elsewhere. Nos. 2 and 3 are reasonably popular pages. No. 4 is a page that nobody goes to; it's a subdirectory index page leading to-- among other things-- one of the most popular pages, but never visited in its own right. And so on.
Definitely no relationship to the listed pages' overall frequency in search results, or the number of sitewide keywords, or click-throughs from google.
Answer #1: It's something so embarrassingly obvious we will both be kicking ourselves.
Answer #2: It's some arcane, mysterious and hitherto unsuspected component of the g### algorithm.