Some investors and economists have been saying for several years that there is an "everything bubble" that inflated in the ZIRP era–stocks, bonds, real estate, art, etc. Asset prices completely detached from their underlying intrinsic value. The belief is that zero interest rates have caused the inflation, and with the end of ZIRP, prices will collapse. Earliest reference to the term I can find dates back to 2017. To my knowledge, Jeremy Grantham, a famous investor, is the most prominent advocate of this theory.