Don't know where that statistic comes from, but I'm not going to doubt it. My family is a part of the community of a very active parish in North TX. It has grown from a few hundred families to over 6,000 in the course of the past 15 years.
Once our new church was finished, I ran the numbers. If every weekend Mass was full, which they weren't, an additional 5 masses would be needed for the rest of the community. So I guess we're doing better than the national average.
I am not a cradle Catholic, nor do I attend Mass every week (I miss 3-4 times a year). But I do wonder why attendance is so poor, when attending weekly Mass is so important.