‘Nobody knows anything’ and ‘this time is different’: the phrases that define — and haunt — the AI economy

There are two phrases that have reliably marked every great financial bubble in modern history. The first is “this time is different” — what Sir John Templeton called “among the four most costly words in the annals of investing,” the signal that investors have begun rationalizing sky-high valuations by convincing themselves that old metrics no longer apply. Carmen Reinhart and Kenneth Rogoff gave the phrase its academic weight in their landmark 2009 book This Time Is Different: Eight Centuries of Financial Folly, documenting how governments and investors had repeatedly convinced themselves that past crises wouldn’t recur — and were always proven wrong. The second phrase is less discussed but equally diagnostic: “nobody knows anything.” It is what you say when the honest position is uncertainty so complete it borders on paralysis. In May 2026, both phrases are everywhere. And remarkably, they are often coming from the same mouths. “Nobody knows anything,” said Ethan Mollick, the Wharton professor and one of the most closely followed voices on AI in the world, speaking to several hundred corporate leaders at the New York Public Library on Thursday morning. “I spend my time talking to AI labs, famous people, I talk to CEOs all the time, and nobody knows anything. We’re all making this up as we go along. So anyone who’s like, ‘We have the playbook’ — they’re lying to you.” The Number Behind the Noise Start with the number that puts all of it in perspective: 0.1%. That is Bank of America’s own estimate for how much AI is currently lifting economy-wide productivity per year — published in the same report that called AI bigger than electricity and the internet combined. Similarly, Goldman Sachs found “no meaningful relationship between AI and productivity at the economy-wide level” in March, while simultaneously reporting a median 30% productivity boost in the