I was just looking through a series of different openings using the Book Explorer, and was wondering how the popularity figure for each opening was figured?  I didn't see any explanation during a quick search of the site/forums.

Thanks in advance,

Mike

Good question, a fairly common line for the QGA was in one of the last pages when sorted for popularity...wonder what the sorting criteria is.

Popularity is usually based on number of games played and how recent the games are.  For game explorer itself I cannot speak.