[gutvol-d] Cumulative download statistics

In answer to my own (lazy) question, plus a couple of unasked ones: * The 1000 most downloaded titles account for 41% of total downloads. * The 10000 most downloaded titles account for 80% of total downloads. * 50% of total downloads are accounted for by the first 1800 most downloaded titles. Graph here if you are interested: http://www.hursts.eclipse.co.uk/pg-cumulative-downloads.pdf