Folk rock peaked in '70s. Commercial chart toppers The Weavers and Harry Belafonte were the '40-50s. North American 'folk revival/craze' calypso (Yellow Bird; John B. Sail; Day-O!; Big Bamboo &c) 'revived' nothing Caribbean. Like 'em, or not, they're Yank Tin Pan Alley pop songs.

What you wind up tracking is one person's consumer preferences about a genre label. Different consumer, different history. It's not very useful.

No century ever ended with the same genre list, instruments and tech it started off with. The entire marketplace reinvents itself every 15-20 years. It was the Lomax's regular complaint on arrival everywhere they ever went.

If Disney sequels Wimoweh; or Washington, DC needs to reboot This Land is Your Land, you're back in business... until the next new thing comes along.