The CARA organization at Georgetown reports that the level of self-reported Sunday mass attendance hasn’t changed much over the past four years: up at the Jubilee, down again, up after 9/11, down when the sex-abuse scandal went nationwide, and now more or less where it was in late 2000.
Admittedly, the real level of Mass attendance probably doesn’t live up to the 33% figure, but the self-reported number is probably a good indication of trends.