When a whole sector moves

One real day

On Dec 12, 2025 the four big banks all went the same way, while the wider market barely changed.

All four fell, and all fell more than the market. We give no cause here, because we only print one when a saved review of the day states it. The point is the pattern: four companies, one direction, one day.

How often do they move together?

In the last year all four went the same way on 69% of trading days. Had they moved independently, it would have happened about one day in eight, or 12.5%.

Part of that is the wider market, because most stocks follow it when it moves. The rest is banking as a sector: the same rates, the same customers and the same rules.

Why companies move together

The same customers and costs. When steel gets dearer, everyone who buys steel notices.

One report speaks for all. When the first company in a sector reports weak demand, the market assumes the others have the same problem, even before they report.

Money moves between sectors. Some fund managers pick a sector first, then a company. When they sell a sector, several of its companies get sold at once.