[Hermann the Cherusker]

There has probably been a similar decline in the percentage of active Catholics during these same years, but this is harder to measure accurately.

Some dioceses do keep track of this. On the Philadelphia Archdiocesean website, you can see statistics showing a decline in percentage participation in certain areas of the diocese (especially poorer neighborhoods).

[american colleen]

Do they or are they able to keep track of the (resultant?) increase in suburban parishes?

It's kind of a joke for us (media, lefty Catholic journals, and some dioceses) to measure Catholics by the numbers of baptisms and marriages in the parishes. Almost everyone I know was baptized and later married in a Catholic parish but almost all of them do not attend Mass at all.

[Held_to_Ransom]

On the Philadelphia Archdiocesean website, you can see statistics showing a decline in percentage participation in certain areas of the diocese (especially poorer neighborhoods).

At the same time, the Southern Baptists have created about 17 new Churches in these areas during this time frame. Ain't that a kick?