I find it hard to believe most quilters are in that age group. Perhaps the survey didn't reach enough older quilters, in order for them to be properly counted.
I just reread the article. It's in the Sept/Oct 2012 McCall's Quilting magazine, article called "The Birth of Modern Quilting". The article stated "While 58% of modern quilter are between 26-45 years old, over 29% are over the age of 45." I wonder what it makes me at 68!