The US is approaching the end of a "superbubble" spanning across stocks, bonds, real estate and commodities following massive stimulus during the Covid pandemic, potentially leading to the largest markdown of wealth in its history once pessimism returns to rule markets, according to legendary investor Jeremy Grantham.

"We are in what I think of as the vampire phase of the bull market," says the GMO co-founder in a paper on 20 December. "For the first time in the US we have simultaneous bubbles across all major asset classes."