Hmm. Folk does not die, but it does wax and wane. In agricultural societies, it tended to keep an even keel. But in urban areas, there seems to be a need for conscious revival every 30 years. I count the 30's, 60's and 90's as these periods. Add 10 years and we should be in a resurgance. This is based upon American revivals. I don't know what the trends are internationally.