The Bank of England just put a yellow flag on global stocks.
Deputy Governor Sarah Breeden said global stocks appear stretched. The gap between current prices and past norms is wide.
Most of the risk sits in a narrow group of mega-cap names.
Breeden flagged that global stocks now trade well above their long-term average. She linked that to a handful of mega-cap names pulling the whole index higher.
The worry is that a rate shock or a weak earnings print could crack that thin base. If it does, the whole index takes the hit.
She did not say a crash is coming. She said the setup is fragile.
When a few names carry the whole index, that is called narrow leadership. It looks strong on the way up and weak on the way down.
If one of those mega-caps slips, the index slips with it. If two slip at once, the move can get sharp.
That is what Breeden was pointing at.
Valuation is how much investors pay for each dollar of earnings. Right now, that number is high by most long-term measures.
Stocks can stay pricey for a long time if rates fall and earnings grow. They can also fall hard if either of those goes the other way.
The BoE is saying the second path is more likely than most investors are pricing.
The BoE Financial Stability Report covers more than just stocks. It looks at bonds, credit, and bank health.
On stocks, the call was clear. Prices are stretched, and the support base is narrow.
That is a rare thing for a central bank to say out loud. It usually comes with a push for investors to be more careful.
The FTSE 100 is less stretched than the S&P 500 on most measures. But the two markets move together more than they used to.
If the S&P sells off, the FTSE tends to follow. A narrow US mega-cap crack would hit UK portfolios too.
That is why a BoE warning on global stocks matters for UK-focused investors, not just for US ones.
Three things to track from here.
First, earnings season. If the mega-caps miss, the warning gains weight.
Second, rate moves. If yields jump, pricey stocks tend to reset fast. Third, the spread between the top few names and the rest of the index.
A narrowing gap is a good sign. A widening one tends to come before a sharp move.
Past BoE warnings on stocks came with similar language. Some were followed by pullbacks. Some passed with no big move.
The pattern is not a clean guide. But it does tell investors that these calls tend to age well when rates also rise.
If yields drift higher from here, this warning is likely to look prescient. If not, it may fade into the background.
Central banks do not usually call stocks overvalued in print. When they do, it is worth reading carefully.
The BoE put a clear line in its report.
The warning is on the record now.