How narrow a sliver can an economy's growth rest on?
The answer is 93.
Not that the economy grew by 93%—but that 93% of U.S. real GDP growth over the past four quarters, from Q2 2025 through Q1 2026, came from a single category of capital expenditure: information-processing equipment and software investment. That category accounts for less than 4% of total GDP. A corner under 4%, carrying nearly all of the growth. Like a thirty-story building with its entire weight on a single column—a column that is borrowed.
Joachim Klement published this finding on May 19th in the Financial Times, under the headline "The Impossible Maths of the AI Boom." The piece is short; the conclusion, hard: the biggest five spenders in that category—Microsoft, Google, Amazon, Meta, Oracle—when you project their stated capex growth paths to 2030, the implied return on investment is almost universally negative. To earn a 10% return on that capex, they would need an additional $2 to $5 trillion in annual revenue. Their combined revenue today is roughly $1.5 trillion.
The strangest part isn't the numbers themselves—it's that Klement isn't the first person to say this. Last fall, Harvard's Jason Furman ran the same calculation on the same BEA data and got 92%. Two people, six months apart, same method, nearly identical results. The gap between 92% and 93% is seasonal drift, not disagreement. Once is an anomaly. Twice is structure.
And Kevin Warsh has just walked into the Eccles Building.
The Eccles Building, on the southeast corner of Constitution Avenue in Washington, has been Federal Reserve headquarters since 1937. The Senate confirmed Warsh as chair on May 13th. His last time in that building was as a Fed governor from 2006 to 2011—spanning the deepest years of the subprime crisis. The labels from that era: hawk, opponent of quantitative easing, very little patience for asset price bubbles.
Fifteen years later, he's looking at 3.2% headline inflation, 3.4% core, and the Iran war pushing Brent crude to $93 a barrel. Markets had expected him to continue Powell's late-term dovish path. Instead, the implied path on FedWatch began to shift—rate-cut expectations erased, one hike before year-end now the base case at roughly 70% implied probability. Markets are not pricing in data. They are pricing in a person's character.
If 100 basis points actually happened, the discounted cash flows of those five major capex spenders would be warped. Back-of-envelope math: treating the AI capex stack as a long-duration portfolio—modified duration ~4.1 years, WACC ~10%, implied return ~negative 12%—a 75 bp hike equals a 3.1% present-value hit; 100 bp, 4.1%. To get implied returns above zero, 2027 capex guidance must be cut by 14.7% to 15.6%.
Add multiplier effects and the synchronized slowdown of semiconductor foundries, optical modules, data center power infrastructure and other upstream and downstream chains, and the credible GDP drag is 20 to 40 basis points. Extreme scenario: 50 to 70.
The 2027 U.S. GDP growth baseline is only around 1.8%. A 20-to-40 basis point drag implies 1.4% to 1.6%. A 50-to-70 point drag: 1.1% to 1.3%.
This is not merely a valuation question. It is a question about what growth is built on.
History offers four comparable moments. Each is a variation on the same story: one column holding up the whole building, then the column pulled away.
Japan, late 1980s. After the Plaza Accord, the yen appreciated 40%. The BOJ slashed its discount rate to 2.5%, flooding asset markets with liquidity. On November 26, 1987, Noguchi Yukio published an article in Toyo Keizai Weekly using a simple DCF model to show that Tokyo land prices were several multiples above fundamental value. In the article, he used a five-character phrase: "borrowed growth"—借りてきた成長. As light as an autumn leaf. Two years later the BOJ began hiking. Real GDP growth fell from an annual average of 5% to 1.2%. The history books called it the "Lost Decade." What was actually lost was more than twenty years.
U.S. Telecom, 1996–2000. After the Telecommunications Act, "internet traffic doubles every three months"—a claim that originated solely in WorldCom's internal marketing materials, with no independent source—drove $3 billion in investment into $300 billion over four years. Carrier capex grew at a 28% compound rate while revenue grew at only 10%. Global Crossing laid $20 billion of undersea fiber; it sold in bankruptcy for $250 million—a 1.25% recovery rate. WorldCom moved $3.852 billion in operating costs off the income statement and onto the balance sheet, relabeling "costs" as "capital expenditure." This was discovered by Cynthia Cooper, the 38-year-old VP of internal audit, who secretly copied hard drive data at night without authorization. When the dust settled, less than 3% of all fiber laid across America was actually lit. The remaining 97% became "dark fiber," permanently buried underground. The capital returns went to zero.
China after 2008. The ¥4 trillion stimulus expanded through local government financing vehicles—state-owned shells used to bypass central debt restrictions and channel credit into infrastructure. By end of 2018, their interest-bearing debt reached ¥41–51 trillion, or 51%–57% of GDP. By Q1 2019, 78.7% of new bond issuance was purely to repay maturing old debt. Borrow new to repay old: the debt doesn't disappear, it just puts on a new face and keeps living on the books. Bai, Hsieh, and Song showed in a Brookings paper that the stimulus permanently distorted capital allocation—credit directed toward SOEs and local platforms with returns far below the cost of capital, private firms crowded out, total factor productivity stepping down permanently. GDP growth fell from 10.4% to 5.2%. Each year's Government Work Report explained the slowdown as "shifting gears."
U.S. Shale, 2014–2016. New wells lose 60%–90% of production in year one. The whole industry was a treadmill: you're not moving forward, you're just stopping yourself from falling back. Average drill-to-breakeven cost above $70/bbl. When oil dropped from $100 to $30, every new well drilled was losing money, and yet you still had to drill. From price peak to capex budget cuts, the lag was only five to six months.
Four episodes. Three countries. Four narratives. Four columns. In each, someone did the math before the collapse: Noguchi Yukio, Cynthia Cooper, Bai Chong-en and Hsieh Chang-tai and Song Zheng, the IEA analysts. Each time their arithmetic was correct. Each time they failed to stop what happened next.
Because what triggers the collapse isn't the arithmetic—it's liquidity, interest rates, oil prices, a central government's policy shift. The arithmetic only provides, after the fact, a way to explain the collapse—so people can say, "We should have seen it coming." But between "should have seen it" and "actually saw it" lies not a failure of sight, but of will.
From the point where underlying returns turn negative to the actual GDP peak-and-decline, the two market-financed episodes—telecom and shale—had lags of only 5 to 10 months. The two with government backing—Japanese real estate and China's LGFVs—stretched to 24 to 30 months.
AI capex is market-financed. No level of government has promised to service their debts. If the trigger comes in H2 2026—Warsh's first rate hike—the window for meaningful contraction falls between Q4 2026 and Q2 2027. The GDP downturn window: H2 2027.
And 2026 has only seven months left.
Five CFOs—Microsoft's Amy Hood, Alphabet's Ruth Porat, Meta's Susan Li, Amazon's Brian Olsavsky, Oracle's Safra Catz—are each deciding the same thing: whether to raise or hold the 2027 capex budget number.
They have all read Klement. Their internal models—broken out by project type, customer type, depreciation curve—reach the same directional conclusion. They have also all seen Anthropic's Q2: $10.9 billion in revenue, a first-ever $559 million operating profit, 5.1% margin. Razor-thin, but the first time a frontier model company has run the number positive.
Yet at the late-July earnings calls, all five will almost certainly say: "We are maintaining our 2027 capex guidance." Because until the first company says "we are cutting capex," no one can be the first. Whoever speaks first admits the game is over.
This is called coordination failure—everyone is holding bad cards, but no one will show first.
In each of the four historical cycles, an exogenous force ultimately broke the equilibrium. For 2026, the candidates include: Warsh's first hike, the Iran war pushing oil to $130, Anthropic's IPO prospectus revealing an unexpected cost structure, or a hyperscaler breaking ranks under pressure from its own internal return-on-capital models. Which comes first? Nobody knows. But whichever it is will set off the same chain reaction.
Klement is not a hero. Neither is Furman. Noguchi's article was published in a magazine still sold at subway newsstands; the 1987 cover was recycled long ago. Cynthia Cooper was named TIME's Person of the Year for 2002; she now lives in Mississippi. Bai is now dean of Tsinghua's School of Economics and Management. The IEA analysts' names are printed on the inside pages of monthly reports—the kind of pages nobody turns to.
None of them are heroes. They simply did the math when it needed doing, said what needed saying. Then the market kept moving at its own pace, until one day it couldn't.
Every capex cycle needs its own arithmetician. And the arithmetician's fate is to be proven right, then forgotten.
The borrowers are still borrowing. The borrowed money has become fiber, copper cable, server racks, GPUs, transformers, coolant—and acres of metal rooftops on the outskirts of Ashburn. Those rooftops reflect a pale, washed-out light in the summer sun, like rows of nameless tombstones, or like envelopes that have not yet been opened.
The time for repayment has not yet come.
But that Table 1.5.2 will keep updating. Once every quarter.
It will not lie.
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