This is unprecedented because it's simply not true. The best statistic I could find for this is 11%. Even 11% seems like a very high number based on my personal experience. As an American who has lived in different parts of America my whole life (and currently living in a high-tourist city with people from all over the US), I can say that most people in most parts of the US do not believe that the rapture will happen within their lifetime.
http://www.publicpolicypolling.com/pdf/PPP_Release_US_0602.p...