The percentage spent on GDP changes very slowly up until 2060. It's still around 3.14% until we reach basically around 2045. Then it starts to.... There are going to be differences. You're using different kinds of statistics but they both show the same pattern. It does decrease, but at a very slow rate, just like the number of seniors continues to increase over that time period.
On May 17th, 2012. See this statement in context.