How is this sort order determined? Is it ranked by popularity, number of results, or a mysterious google algorithm? Does there algorithm take into account the search popularity of a query (using google-trends data or something)?
Edit: I found a news article dating back to when google suggest was made public in 2004. Here is an excerpt...
How does it work? "Our algorithms use a wide range of information to predict the queries users are most likely to want to see. For example, Google Suggest uses data about the overall popularity of various searches to help rank the refinements it offers."