The Roman Catholic

I quoted THE WORLD ALMANAC 2004.
Vatican City 99%
Italy Predominately
Andorra Predominately
Honduras 97%
Venezuela 96%
Bolivia 95%
Ecuador 95%
Poland 95%
Portugal 94%
Spain 94%
Argentina 92%
Ireland 92%
Malta 91%
Colombia 90%
East Timor 90%
Monaco 90%
Paraguay 90%
Peru 90%
Saint Lucia 90%
Chile 89%
Mexico 89%
Croatia 88%
Ceychelles 87%
El Salvador 85%
France 85%
Nicaragua 85%
Panama 85%
Philippines 83%
Brazil 80%
Haiti 80%
Liechtenstein 80%
Equitorial Guinea Many
Luxembourg Many
Austria 78%
Dominica 77%
Costa Rica 75%
Belgium 75%
Slovenia 71%
Hungary 68%
Burundi 62%
Slovakia 60%
Rwanda 57%
Grenada 53%
Kiribati 52%
Belize 50%
Congo Wikipedia 50%
Micronesia 50%
Palau 49%
Canada 46%
Switzerland 46%
Czech Republic 39%
Angola 38%
Germany 34%
Nauru 33%
Uganda 33%
Netherlands 31%
Trinidad and Tobago 29%
United States 28%
Australia 26%
Central African Republic 25%
Suriname 23%