Geopolitics risk-off · 0–6 months
A what‑if from the future

What if Iran mines and fully closes the Strait of Hormuz?

Iran re-mining and closing Hormuz is the batch's maximal oil shock -- ~20mbd (a fifth of global supply) at stake -- so the +9% Brent, +7.7% deleveraging and +2.6% inflation-expectations legs are all correctly outsized. Rhymes with the 1987-88 Tanker War and the June 2025 12-Day War scare, when mere closure threats added double-digit risk premia. Transmission: Asia (China, India, Japan, Korea) imports the bulk of Gulf crude and is most exposed; the US is now a net exporter and more insulated. Forward: a true full closure is unprecedented and self-harming for Iran, so duration -- not the initial spike -- is the key uncertainty.

9%
our model probability
over 0–6 months
prediction markets — the market's odds
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Anchored to measured history 9% · 90% range 1–16% · 40 dated precedents behind it — a wider range means thinner evidence

Every number ships with its receipt — the odds, the range, the precedents, and a public grade at Reality Check. The statistical machinery that produces it is proprietary.

The butterfly cascade

How this trigger trickles across markets, left → right — the root shock, its first‑order moves, then the ripple effects. Drag any node; tap a market for its real price history.

Resolution timeline — how this probability is moving

Our model's odds (electric blue) over time vs the market's (Polymarket, amber), from the past toward the 0–6 months horizon. Each dot is a real macro event that nudged the probability — green pushed it up, red pushed it down. Tap a dot for the source. Loading the probability audit trail…

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What it would mean

If this plays out, it is a risk-off shock. After June's reopening, Iran re-mines the strait and seizes a tanker convoy, fully closing Hormuz to traffic and detonating shipping-insurance and crude markets. The trigger decomposes into signed root‑shocks — Geopolitical risk ▲ · Oil supply risk ▲ — which propagate through our causal graph to the markets below.

Methodology. Probability and impact are anchored to history and scored against what actually happens — wins and losses, in public, at Reality Check. Market odds live from Polymarket & Kalshi. By Vikas Singh, Quantitative Strategist. Updated 2026-08-13.