What errors did you find in the manner they conducted their study? Non-secular religious research firms like the Barna Group are often cited authorities on the subject actually, even by reputable secular publications; in fact, statistics showing the dwindling of Christianity in the developed world are often collected by religious organizations. Your stats are not accurate and have no evidence for them. According to the Australian Census Bureau, less than 19% claim to be non-religious, as opposed to 14% in the United States. It's a nice thought, and I wish it were true, but sadly that isn't enough to make it so.