There is naturally a strong U.S bias. Results can be 'contaminated,' e.g. if one collector searches daily for his favourite author or if a dealer has a single author collection that is frequently accessed. Results were surprising often because of the authors who failed to get a significant showing. Christie, Wodehouse, Fleming-the triumvirate of collectible Brits have a very low profile and do not make my lists. Churchill gets there, but mainly through a person or persons unknown searching for 'The World Crisis'-most likely the elusive volume six.
Findings are thus somewhat conjectural, but a definite tendency is discernible.
See for yourself. High Baum, Doyle, Hiaasen, Heinlein, John McPhee, AA Milne, Tolkien, Ayn Rand, Vita Sackville-West, Susanna Moore, Jules Verne. Dealers who stock all of the above are on the right track in cyberspace. This is a mixed bunch. It was established by an eccentric semi-genius by the name of Richard Booth in 1961.