Why the editor chose the PEN/O.Henry winning stories

A scan of the table of contents (or back cover) of the "Pen/O.Henry Prize Stories 2010," edited by Laura Furman, shows that really only 3 of the authors are well-known short story writers: Annie Proulx, William Trevor, and Alice Munro. Trevor and Munro are included no doubt because their stories are great and certainly because they're the two greatest living short-story writers in the English language (and yet: weren't the O.Henry awards at one time limited to U.S. authors? Or at most to North American? Aren't there about 60 million UK and Canadian literary prizes? What's wrong with having a U.S. short-story award?). Proulx included on strength of her story (Old Cowboy Songs) for sure and also on her literary prowess. The others? Great to see that the editors were not driven by name-value, high recognition. At worst, maybe there was some logrolling (what? in a literary award? shocking!) but I have no evidence of that - so let's assume all of the other stories were selected on the merits. (One year the Best American Short Stories were selected blind - great idea!) Would be fun to ponder, reading through the collection, why the editors selected each one. Read Kristen Allio's "Clothed, Female Figure," which I think drew attention because of its unusual and sustained narrative technique - story told by an older Russian "nanny" regarding letters she is receiving from one of her former charges now a "nanny" herself - the interior letters are much more in an author's voice (Bennington girl, artist) than the main narrator (unschooled, nonnative speaker/writer), so the story seems to be in a reverse frame - we know more about the letter writer and very little, just hints, about the life of the narrator. By the way: why do the PEN/O.Henry Awards list only a few (this year, only one!) runners-up? It's like saying somebody liked your story but we just could not even bring ourselves to publishing it with these other 20 - a long list of runners-up at least shows that there was a two-stage selection process.