How committed to religion are people? This is rather difficult to establish as surveys can be biased by social pressure. For example, it is nowadays perfectly acceptable to be an atheist in Europe, but an atheist would be a social outcast in many parts of the United States. Hence, many stay in the closet in the US and are not visible, for example by still attending church because of social pressure or because it is the only social activity in their area.
As so often, actions are more revealing than opinions. Fernando Lozano uses an indirect indicators of religiosity that is based of economic choices: working hours on religious holidays over the last 30 years in the US. A few interesting trends emerge: Jewish holidays have become more observed, while Christian ones have become more observed if they have been secularized (like St. Patrick) and less if not (Good Friday). This is consistent with the renewal of Judaism and the commercialization of Christian holidays.