What happened
Grantham, co-founder of Boston-based asset manager GMO, used the phrase 'proof of unnecessary work' to describe Bitcoin in comments surfaced Friday by BeInCrypto. The wordplay targets proof-of-work, the consensus mechanism that requires miners to expend electricity to validate transactions and mint new coins. Grantham went further, predicting the broader crypto market would dwindle over the coming decades rather than scale into a mainstream asset class.
He didn't put a price target on the call and he didn't name a timeline beyond 'decades. ' GMO, which Grantham co-founded in 1977, managed roughly $60 billion in client assets at last public disclosure and has no listed Bitcoin exposure. Grantham himself built his reputation calling the 2000 dot-com top and the 2008 housing top, and has spent the past four years warning that US equities sit inside what he calls a 'superbubble.
' Bitcoin, in his framing Friday, is a smaller appendage of that same speculative excess.
Why it matters
Grantham is not a crypto-native commentator and he doesn't move price on a single soundbite. He matters because allocators read him. His quarterly letters circulate inside pension funds, family offices, and endowment investment committees that have spent the past 18 months debating whether to add a Bitcoin sleeve through spot ETFs.
A line like 'proof of unnecessary work' is engineered to travel, and it gives sceptical CIOs cover to keep saying no. The contrast with current flow data is sharp. Spot Bitcoin ETFs have pulled in tens of billions in net subscriptions since launching in January 2024, and the issuer roster now includes BlackRock, Fidelity, and Franklin Templeton, three of the largest fund houses on the planet.