I don't have the studies in front of me, but religion isn't actually dying per se. Like all other things, it's becoming modernized, which means people are taking more individual control over their spirituality. The euphemism for Catholics is "cafeteria Catholics" because they pick and choose the parts of the doctrine that has the most meaning to them. Many of these people have personal religiosity and spirituality that they feel doesn't fit with the large organized churches, but are still very much religious in an individual way. This is difficult to capture because they will often respond "no religion," as in they're not affiliated with any particular Church, sect, or congregation, but they are indeed religious in a modernized way. Society is becoming more liberal (as in individual liberties and freedoms) and this is just another area where individuality and freedom of choice has changed social organization.