The Bank for International Settlements just compared the AI boom to the railway mania of the 1840s and the dot-com bubble.

Here is what the BIS actually said.
The five largest hyperscalers, Microsoft, Google, Amazon, Meta, and Apple, are on course to spend more than $1 trillion on AI infrastructure across 2025 and 2026 combined. Capex as a share of revenue has now blown past every historical benchmark for large firms, and the gap is still widening. The dotted forecast line in their own chart goes nearly vertical.
Look at chart C. Chart C in the BIS report is the one worth staring at.
Every major technology investment boom in history, canal mania, railway mania, electrification in the 1920s, dot-com, all peaked between years 3 and 5 at roughly 3 to 4x their pre-boom trough, then collapsed hard enough to take entire economies with them.
The AI boom is the black line.
It's currently tracking steeper than every single one of them at year 3.
The BIS isn't saying AI fails. It's saying the shape of this curve has never resolved gently in recorded history, and that $1 trillion in hyperscaler capex funded increasingly by debt means the reversal, if it comes, doesn't stay in equity markets.
It moves through every company that builds data centers, supplies chips, or borrowed money assuming the contracts keep coming.
The dot-com bust hurt investors. This one has a plumbing problem underneath it.