“We’ve never had as many currencies in negative interest rates. $17 trillion worth of bonds [are] in negative interest rates. It’s never existed before. And, that’s a bubble. So, we’re in the biggest bond bubble in history, and it’s going to burst“

Paul said 
https://www.zerohedge.com/economics/ron-paul-warns-us-rates-are-going-negative-fed-cant-stop-it