I don’t know if you are asking, how full is the Church at each Mass (all except 7:30 am are packed during the school year, Noon -youth- Mass is out the door)
or are you asking how many registered parishioners attend Mass?
We have 3000 familis on the computer who registered at some point in time. we print 1000 bulletins a week, and they are all gone by the end of Sunday. Our church seats about 320 when it is at capacity. In consulting the university experts who have studied demographics of our town, in preparation for an evangelization program and a capital campaign for the new church, we found that: our town has a population of 28,000, there are estimated 18,000 self-identified Catholics in the town. There are 3 parishes. If 1000 attend Sunday Mass at each parish, that is 3000. Even if you assume that an additional 3000 attend Mass at neighboring parishes or the Basilica, that leaves 12,000 self-identified Catholics sleeping in at home, possibly working or traveling, or attending churches of other denominations.
sounds like our evangeliation-to-Catholics proposal is long overdue.