What the statistics don't show is the the country of origin for the people starting from each location. However I have a theory that goes like this:
More Spaniards are starting in the traditional starting locations like O'Cebreiro and Sarria since to due the current economic conditions this is the most affordable solution that allows them to at least walk the camino, and earn an Compostela (which is good for the résumé), as compared to starting somewhere further east like Burgos or Leon. My experience also suggests most Spaniards are in the 30-60 age group, and again they can only afford a limited time off to walk the camino due to family and work commitments. The drop in the number of Spaniards from approx 70% to under 50% reflects this significant change.
Likewise more experienced pilgrims (those that have walked the
camino Frances already) will more than likely try another route, typically from my experience, the Portuguese route or Camino Primitivo or Camino Norte. Just following the threads of conversations on this forum suggest these routes are common alternatives to the
camino Frances route. The rise in the number of people walking the other routes as a percentage, reflects this change, though it is not significant.
The newbies (those that have never walked the camino) are started where many of us did before, in places like Saint Jean or Roncesvalles, or even Pamplona. More and more of the newbies are arriving from native English speaking conuntries like the USA, Australia and the New Zealand. Given the distance involved most make this "the trip of a life time", taking off more time to walk a longer distance. I would also suggest that many of the newbies are boomers which itself is mostly an American, Canadian, Australian and New Zealand demographic. Boomers are described as wealthier, healthy and more traveled than any other age group before them, and thus might be described as having the luxury and time to travel the longer distances for longer times.
Saint Jean, Roncesvalles and Pamplona are ideal gateways to people arriving from outside Europe. Both the significant rise in the number of people from native English speaking countries and the number of people starting in places like Saint Jean, Roncesvalles and Pamplona reflect this significant change.