The AI Bid Is Eating Its Own Marginal Buyer

The bull case for US equities rests on a quiet circular flow: foreign dollar surpluses recycled into mega-cap tech, domestic wage income passively bid into the same names, and credit spreads loose enough to keep the marginal buyer levered. AI threatens each leg simultaneously. That is the structural risk the Bank of England's Financial Policy Committee is now flagging in its own language, and which Capital Flows has been arguing with more force: the melt-up and the eventual break are the same trade.

Start with valuations. The FPC's June record is unusually direct, singling out US AI-exposed technology as the segment where pricing has detached from a plausible distribution of outcomes. That matters less as a forecast than as a description of fragility: when a narrow cohort carries index-level duration, any repricing in the AI capex thesis transmits directly into pension balance sheets, sovereign wealth allocations and the levered private credit structures financing the build-out. The Committee's warning that vulnerabilities could crystallise simultaneously is not boilerplate. It is a statement that the correlations investors assume will diversify them have collapsed.

The more interesting argument, and the one underpriced by sell-side strategy desks, is structural rather than cyclical. Capital Flows' thesis is that AI and reshoring are rewriting the income statement of the US household and the balance sheet of the foreign buyer at the same time. Autonomous manufacturing reduces the wage bill that feeds 401(k) flows. Domestic production reduces the trade deficit that has, for two decades, recycled into Treasuries and mega-cap equity. The marginal buyer of US assets is being automated away by the very technology those assets are priced on.

A system short volatility by construction

Layer on the credit channel. The FPC notes that sovereign debt markets are now characterised by concentrated leverage among a small number of hedge funds running similar relative-value strategies across jurisdictions. That is the same plumbing that broke in March 2020 and again, in a different guise, during the 2022 gilt episode. Private credit is the newer worry: a vehicle that has absorbed risk-transfer from regulated banks without yet being tested through a default cycle. If the AI capex narrative wobbles while energy prices remain elevated from the Middle East shock, the FPC's simultaneous-crystallisation scenario is not tail risk. It is the base case of a stress test.

“If you are driving productivity, will we end up having way more stuff than we consume? And then if we shift to a new type of system, will this begin to change how capital flows through the system for the channels of macro liquidity and credit?”

— David Friedberg

The policy implication is uncomfortable. Capital Flows' framing — that the credit cycle is economic statecraft and that no Western government can afford a recession while China stands ready to absorb industrial share — suggests authorities will lean against any meaningful tightening of financial conditions. That is bullish in the near term and structurally bearish further out, because it means the imbalances compound rather than vent. Traders pricing the next twelve months should distinguish between the regime in which the bid persists and the regime in which it doesn't. The catalyst between them is unlikely to be a rate decision. It will be a credit event, and the FPC has already named where to look.