Elon Musk says AI is the only way to fix the $40 trillion U.S. debt crisis—but a new study says even the most optimistic scenario won’t fill the hole

In the great debate about rebalancing the United States’ debt to its economic growth, the optimists suggest that expanding the economy is preferable to cutting federal spending. It would certainly be less painful.
Indeed, SpaceX founder CEO Elon Musk has suggested that the productivity gains thanks to AI may be the only way to save Uncle Sam from his growing debt burden—$39.5 trillion at the time of writing.
Musk, the CEO of Tesla, has long been a debt hawk, even if it meant going against President Trump on the matter. Musk told the Nikhil Kamath podcast last year that AI and robotics used on a large scale is “pretty much the only thing that’s going to solve the U.S. debt crisis.”

But new research from Brookings, authored by Ben Harris, Neil R. Mehrotra and William Overcash, suggests that while AI-driven economic growth might meaningfully shrink fiscal deficits, it is still unlikely to bridge the gap “even in more optimistic scenarios fully.”

The suggestion that AI could be the silver bullet for a fiscal crisis is understandable, the trio writes, owing to the active capital expenditure into the transformative technology thus far, as well as “the unharnessed capacity of the technology to boost productivity.”

Indeed, AI investment has continued at such a pace this year that it’s taking even Wall Street analysts by surprise. For example, BNP Paribas lifted its near-term U.S. GDP growth estimates earlier this year on the back of capex announcements indicating a larger impulse from the AI buildout than the banking giant had expected. While they estimated that growth for all of 2026 will stay the same at 2.6%, the markets team highlighted that on a Q4/Q4 comparison of this year to last, growth would be 2.6% rather than the 2.1% previously estimated.

Likewise, AI—even in its early years of testing and adoption—seems to be having an impact on output. A June study from The Centre for Economic Policy Research (CEPR) found that the implied measure of AI-attributed labor productivity growth (derived from revenues and employment) for 2026 is 1.8%—gains are expected to be highest in high-skill services and finance, where they exceed 2%.

AI could also meaningfully impact some of the most expensive aspects of the fiscal outlook: Outlays for Medicare and Medicaid in 2026 are expected to be $674 billion and $472 billion, respectively, according to estimates from the Congressional Budget Office. The report suggests that, in a positive scenario, AI could have a meaningful impact on the outlook because “the healthcare sector exhibits substantial misallocation and inefficiency that a productivity shock could reduce.”

Likewise—in a perfect scenario—AI could lead to a more lucrative taxable workforce, the authors add: “Productivity growth tends to translate into higher tax revenues primarily through tax base expansion, with long-run responsiveness close to proportional in most advanced and emerging economies.”

A victim of its own success

However, even though the groundwork for a debt resolution in the form of a “once-in-a-lifetime” productivity boom appears to have been laid—across financing, early productivity gains, and efficiency and revenue opportunities—the Brookings report suggests that an AI productivity shock may mean the U.S. economy becomes a victim of its own success.

A “traditional” productivity shock would be positive for the debt picture, the trio writes: primary deficits turn negative, the annual deficit falls by over $2 trillion, and deficit as a share of GDP declines by almost 5 percentage points. “Here, the techno-optimists are validated,” the authors add.

However, AI has the potential to be so transformative that it “should give optimists pause,” the economists note. The first factor is that efficiencies in healthcare, which translate to lower costs, also mean that societies are likely to live longer and will draw more heavily on social security support as a result.

Additionally, the report suggests the much-feared labor market shift means more unemployment, and more individuals relying on income support payments as the dust settles. Defense spending is also likely to increase as countries seek to win the AI arms race.

Next, the authors write: “A changing composition of national income may push the tax base away from highly taxed labor income to less-taxed non-corporate capital and corporate profits. And lastly, increased demands for investment may raise the neutral rate of interest, which pushes up equilibrium interest rates and boosts interest expenditures.”

As a result, while AI will improve the budget outlook somewhat, it can’t be relied upon to solve the U.S.’s fiscal problem. The team found that, at best, these factors offset AI’s potential to reduce budget deficits by half. At worst, these mitigating factors would knock two-thirds off any improvement.

This story was originally featured on Fortune.com