What is shared-driver risk?
Shared-driver risk is hidden concentration: when several positions you think are diversified actually depend on the same underlying thesis, so they break together. Two different tickers, one point of failure.
Also called: hidden correlation, thesis concentration, same-driver risk
Diversified on paper, concentrated in reality
A portfolio can hold a dozen names and still be a single bet. If five of them rely on the same driver (AI data-center capex, a low-rate environment, one regulatory outcome) then a single event breaks five theses at once. The ticker-level diversification is real; the thesis-level diversification is an illusion.
Shared-driver risk is invisible to allocation charts, which group by sector or asset class, not by the reason each position works. It only shows up when you map positions to the thesis pillars underneath them and notice the same pillar appearing across supposedly unrelated holdings.
Common questions
How is shared-driver risk different from concentration risk?
Concentration risk is usually measured by position size or sector weight. Shared-driver risk is measured by the reasons behind positions: distinct holdings that depend on the same thesis driver and therefore fail together, even when no single position looks too large.
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