Just reading through the ATC's publication AT Journeys Sept/Oct and figured I would share this nugget : "The Harpers Ferry Visitors Center photographed a record 1,012 northbound thru-hikers this year--passing the 1,000 mark for the first time (2011 set a record with 849)."
It goes on to talk about the growing # of starting and half-way hikers. I am guessing the good weather this year explains some of the increase with the general long term growth trend explaining the rest.