A new market analysis argues today's stock market is more dangerously overvalued than it was right before the 1929 crash, and warns the comedown could be sudden rather than a slow grind lower.

• Stock valuations by several measures (price-to-GDP, Schiller CAPE) are now higher than in 1929 and near levels seen at the peak of the dot-com bubble, meaning stocks are historically expensive and have a long way to fall if they correct.
• Borrowing to buy stocks is cheaper today relative to dividends than it was in 1929, which encourages even more leveraged buying — a risk that was central to the 1929 crash.
• The economy is now propped up heavily by AI company spending, and that spending is increasingly funded by debt and new stock sales rather than profits; big AI players like OpenAI and Anthropic are losing tens of billions of dollars a year, and some AI-linked companies' debt insurance costs are spiking, a sign markets see real default risk.
• The argument is that if AI company spending slows, it drags down both the stock market (dominated by a handful of AI-tied giants) and the broader economy at the same time, unlike the dot-com bust or 2008, when the economy wasn't as dependent on asset prices.
• Historically, sudden "reset" style crashes (1929, 1987) wiped out a quarter of the market's value in days, versus 2008's slower multi-month decline — the warning is that this time could look more like the fast version.

Outlook: No crash has happened yet, but the analysis flags growing stress in AI-related corporate debt as an early warning sign worth watching closely in the coming months.