I don't get the basis for the thread, to be honest. But here are the US statistics - I would say that millions believe it Catholicism.
http://cara.georgetown.edu/bulletin/index.htm
U.S. Data | 1965 | 1975 | 1985 | 1995 | 2000 | 2005 | 2006 * |
Diocesan priests | 35,925 | 36,005 | 35,052 | 32,349 | 30,607 | 28,702 | 28,299 |
Religious priests | 22,707 | 22,904 | 22,265 | 16,705 | 15,092 | 14,137 | 13,495 |
Total priests | 58,632 | 58,909 | 57,317 | 49,054 | 45,699 | 42,839 | 41,794 |
Priestly ordinations | 994 | 771 | 533 | 511 | 442 | 454 | 431 |
Graduate-level seminarians | 8,325 | 5,279 | 4,063 | 3,172 | 3,474 | 3,308 | 3,306 |
Permanent deacons | -- | 898 | 7,204 | 10,932 | 12,378 | 14,574 | 14,795 |
Religious brothers | 12,271 | 8,625 | 7,544 | 6,535 | 5,662 | 5,451 | 5,181 |
Religious sisters | 179,954 | 135,225 | 115,386 | 90,809 | 79,814 | 68,634 | 66,608 |
Parishes | 17,637 | 18,515 | 19,244 | 19,331 | 19,236 | 18,891 | 18,584 |
Without a resident priest pastor | 549 | 702 | 1,051 | 2,161 | 2,843 | 3,251 | 3,405 |
Catholic population | 45.6m | 48.7m | 52.3m | 57.4m | 59.9m | 64.8m | 64.0m |
Percent of U.S. population | 24% | 23% | 23% | 23% | 22% | 23% | 22% |
Catholic elementary schools | -- | -- | -- | 6,979 | 6,923 | 6,574 | 6,386 |
Students in Catholic elementary schools | -- | -- | -- | 1.991m | 2.013m | 1.779m | 1.727m |
Catholic secondary schools | -- | -- | -- | 1,238 | 1,221 | 1,225 | 1,203 |
Students in Catholic secondary schools | -- | -- | -- | 614,571 | 639,954 | 640,952 | 636,447 |
Gallup Poll: Yearly average percent of U.S.adult Catholics who say they attended Mass in the last seven days ( i.e. , those attending in any given week). | 67% | 54% | 53% | 47% | 52% | 45% (2004) | -- |
CARA Catholic Poll (CCP): Yearly average percent of U.S.adult Catholics who say they attended Mass once a week or more ( i.e. , those attending every week). | -- | -- | -- | -- | 33% | 35% | 36% |
*The 2006 numbers do not include the Archdiocese of New Orleans, due to Hurricane Katrina |
World Data | 1970 | 1975 | 1980 | 1985 | 1990 | 1995 | 2000 | 2004 |
Diocesan priests | 270,924 | 259,331 | 257,409 | 253,319 | 257,696 | 262,418 | 265,781 | 268,041 |
Religious priests | 148,804 | 145,452 | 156,191 | 150,161 | 145,477 | 142,332 | 139,397 | 137,409 |
Total priests | 419,728 | 404,783 | 413,600 | 403,480 | 403,173 | 404,750 | 405,178 | 405,450 |
Diocesan priestly ordinations | 4,622 | 4,140 | 3,860 | 4,822 | 5,938 | 6,444 | 6,814 | -- |
Graduate-level seminarians | -- | -- | 33,731 | 43,476 | 51,603 | 54,154 | 55,968 | -- |
Permanent deacons | 309 | 2,686 | 7,654 | 12,541 | 17,525 | 22,390 | 27,824 | 31,524 |
Religious brothers | 79,408 | 70,388 | 73,090 | 65,208 | 62,526 | 59,515 | 55,057 | 54,620 |
Religious sisters | 1,004,304 | 968,526 | 960,991 | 917,432 | 882,111 | 837,961 | 801,185 | 776,269 |
Parishes | 191,398 | 200,116 | 206,503 | 212,021 | 215,805 | 220,077 | 218,196 | 219,655 |
Without a resident priest pastor | 39,431 | 46,074 | 50,469 | 55,343 | 57,664 | 60,705 | 55,729 | -- |
Catholic population | 653.6m | 709.6m | 783.7m | 852.0m | 928.5m | 989.4m | 1.045b | 1.114b |
Percent of world population | 18% | 17% | 18% | 18% | 18% | 17% | 17% | 17% |
International Mass Attendance: Population weighted percentage of adult Catholics who say they attended Mass once a week or more ( i.e. , those attending every week) in the 38 largest Catholic population nations. | -- | -- | -- | -- | -- | -- | 41% | -- |