2025 AI热潮的理性评估报告（英）

06 November 2025 WHERE DO BUBBLES COME FROM? There is no simple metric that allows us to identify bubbles in real time, let alone assess their magnitude and likely duration. But bubbles do have common features, which means we can look to history as a guide for probable “markers”. Whether it’s merchants trading tulips in 17th century Amsterdam or the 90s dotcom euphoria, there are lessons to be learned for today’s AI boom. WHEN BUBBLES BURST It is tempting to blame bubbles on central banks. The popular trope is that bubble-type exuberance appears only during periods of “easy money”. That isn’t necessarily true. What we do know is that central banks can influence what happens when a bubble bursts (within reason) and that they have a habit of marking the peak of the bubble with a sudden bout of hawkishness. LESSONS FOR THE AI 'BUBBLE' Monetary tightening certainly has the potential to burst the AI “bubble”– either because a rebound in inflation forces the Fed to pivot or because there is an “accident” in the bond market. But past bubbles point us to other red flags including (i) diminishing returns to AI scaling, (ii) earnings disappointment, (iii) vendor financing, (iv) insider selling, and (v) retail investors going all-in. Macro Picture WHEN WILL THE AI 'BUBBLE' BURST? Dario Perkins With US stocks close to record highs, everyone has been talking about asset-price bubbles. Is the tech sector now a bubble? How can we tell? (What are the markers?) And if this is a bubble, when will it burst and what will be the impact on the global economy? Could it trigger another financial crisis? We look to economic history to provide some answers. Chart 1: The world’s most infamous bubbles Source: TS Lombard 05101520250123456789-12-9-6-3036912151821242730RailwaysSouth Sea1929DotcomMississippiTulips (RHS)asset price, multiple of starting pricemonths from peakMacro Picture | 06 November 2025 2 WHEN WILL THE AI 'BUBBLE' BURST? History is littered with financial bubbles – that is, big increases in the prices of assets, such as stocks and real estate, that become detached from fundamentals and suffer massive reversals. In the 1630s, it was merchants trading tulips in the taverns of Haarlem and Amsterdam. In the 1720s, it was companies in France and Britain that promised access to the riches of the New World. In the 1800s, it was railway mania. And, of course, the modern era gave us the Roaring Twenties, Japan’s property crash in the 1990s, dotcom and the subprime bust (you might remember that one…). While all bubbles are obvious in retrospect, identifying them in real time is much tougher. There is no simple metric, while those often touted as the answer – such as the ratio of stock prices to GDP or cyclically adjusted PE ratios – have been flashing warning signals for years without delivering the promised reversion to mean. What we do know, however, is that most bubbles follow a similar pattern and there are some “markers” that point to when things are getting out