That makes this bill of health look a lot more precarious.

The annual number crunch by business consultants McKinsey & Company tries to capture the global financial picture using a balance sheet lens, estimating the scale of interlocking assets, liabilities and wealth around the world.

National variations can be stark, but the overall picture is clearly one of household net wealth expanding faster than global gross domestic product.

Equities were the main driver of this in all major economies last year. The artificial intelligence boom swept world equities 20 percent higher last year, even in the face of seismic United States trade disruptions and even as real GDP growth hovered near its long-term average.

The McKinsey report said household wealth expanded 7.3 percent globally last year, well above the 5.9 percent annual average since 2000. Some 57 percent of that gain was because of equities, with only 15 percent driven by real estate, a marked departure from the average composition of wealth drivers over the past 25 years during which real estate produced more than half of the increase in wealth.

To put that in context, real estate currently accounts for about half of global household net wealth. Equities and investment funds represent about a quarter, with 20 percent in bonds and pensions and 20 percent in cash deposits. Loans of roughly 15 percent subtract from the total. The equity percentage is a bit higher - closer to a third - in the US.

All well and good then, unless you think that equity markets are seriously out of whack and riding for a fall.

And this is where the report's authors focus their anxieties, fretting about stocks' "mounting detachment" from the real global economy, the risks of a sharp correction and rising inequality in asset holdings.

Last year, for example, US equity values soared to 2.4 times corporate net assets, with profits' share of US GDP now double their level in 2000.

Paper gains were the lion's share of the $40 trillion rise in household wealth last year. Only 20 percent was based on net new investment - in real assets including machinery and equipment, homes and buildings, infrastructure and intellectual property, less depreciation - compared to 30 percent on average from 2000 to 2024. Valuations of existing assets grew 4 percentage points faster than already-high inflation.

"When the balance sheet outruns the underlying economy, weaknesses can be exposed," McKinsey said. "When real estate and equity values rise faster than GDP, capital may disproportionately go to asset repurchases, sometimes with a lot of leverage. This may push up valuations but leave the economy deprived of the type of investment that generates long-run growth."

"For households, wealth rises but merely on paper, with heightened risks of eventual corrections. Growing asset values also tend to exacerbate wealth inequality, as existing owners of wealth see large gains while entering asset markets becomes harder for others - for example, young households trying to buy a home."

These problems are well documented but speak to the question of the moment. Will the blistering AI-driven stock market surge and capex spree of recent years be justified by the real returns and productivity gains over the long term?

That question is causing more angst than usual this week as the major AI "hyperscalers" report earnings.

If there's even a reasonable doubt that these equity valuations are justified, their reversal could ripple far and wide.

On one level, the equity issue is very US-centric, with the US accounting for nearly half of the equity held across all countries in the McKinsey sample. And US equity values climbed to 2.4 times net assets last year while the figure in most other countries hovered around 1.0.

But a US equity pullback would affect households around the globe too. More than one-third of US equity liabilities are owed to foreign entities, as is clear in the gigantic deficit in the US net international investment position.

So what's the report's conclusion? It restates its three main scenarios. Either we get the promised productivity miracle that AI cheerleaders tell us is coming, or persistently high inflation eventually erodes real asset values and debts and reconnects the balance sheet with nominal GDP. The third option is a painful correction in which savers and the underlying economy suffer a protracted hangover.

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The writer is a Reuters columnist. The views expressed are personal.