Iran reopened the Strait of Hormuz, then reversed course, prompting the US Navy to seize an Iranian ship. The Polymarket contract on S&P 500 movement for April 17 holds at 100% YES, unchanged despite the tensions.
Market reaction
The S&P 500 April 17 contract prices a fully bullish outlook at 100% YES here. Iran’s policy reversal and the US ship seizure initially spiked oil prices, but the contract hasn’t moved. The April 15 contract is also flat at 100% YES.
Why it matters
At 100% YES on both dates, traders are betting the market absorbs these geopolitical shocks without a meaningful downturn. Buying YES at this level offers no upside, which means traders have priced in essentially zero downside risk from the Hormuz situation. That pricing breaks if energy markets react more sharply to the supply threat or if the confrontation escalates beyond a single ship seizure.
Volume and liquidity
The S&P 500 April 17 contract has volume at $1,351 in daily USDC traded. That’s thin liquidity, but the stability in odds suggests no large orders are pushing the price around. Traders holding positions at 100% appear committed rather than passive.
What to watch
Any further US-Iran military engagements or a second Hormuz closure attempt could force a reassessment. Iran’s next response and whether the US takes additional naval action are the two variables most likely to move these contracts off 100%.
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Spx Opens Up Or Down On April 15 2026| Contract | Odds | Δ since publish | Volume 24h | |
|---|---|---|---|---|
| April 15 | 100% | — | — | Trade → |
| Contract | Odds | Δ since publish | Volume 24h | |
|---|---|---|---|---|
| April 17 | 100% | — | — | Trade → |
