Strait of Hormuz Shipping Markets: What a Transit-Call Contract Counts

A Strait of Hormuz prediction market on Kalshi does not ask whether a ceasefire is holding. It asks whether the number of transit calls in IMF PortWatch, added up over a named Monday-to-Sunday week, is above a stated line. “Above 15” and “above 20” are separate contracts. If the week prints 26, both can pay.

That nested ladder is the detail people miss when they trade the headline. The current example is the week of November 2 through November 8, 2026. The contract language says it will not resolve before Tuesday at 9 a.m. Eastern after the week ends, once the daily counts are complete. The dataset, not the news, is the settlement source.

A transit call is a detected passage, not a cargo story

PortWatch publishes daily chokepoint transit calls from ships’ AIS signals, the satellite tracking broadcasts commercial vessels use. Prediction Scout’s reconstruction of the Kalshi rule describes one transit call as one ship passing the strait, as detected in that dataset. The weekly total is the sum of the seven daily counts. Ships that switch their transponders off are not in the count. A revision PortWatch makes after the contract has expired does not rewrite a settled week.

Those limits are the market. A week can look busy on television and print a lower PortWatch total, or the reverse, because the contract never promised to count unseen ships. The same series exists for the Suez Canal, the Bab el-Mandeb Strait, and the Panama Canal. Each chokepoint has its own typical range. A line that is low for the Panama Canal can be high for Hormuz. Do not carry a threshold from one ticker to another.

The official series pages are the IMF’s PortWatch and Kalshi’s November 2–8 Hormuz event. Read the rung you would actually trade. “Above 15” is not the same position as “above 25.”

Why the ladder is not a one-winner board

Election map markets, like the Senate swing-state board, are mutually exclusive. One combination wins and the others lose. A shipping ladder is nested:

• If the official sum is 18, “above 15” is Yes and “above 20” is No.
• If the sum is 26, “above 15,” “above 20,” and “above 25” can all be Yes, while “above 30” is No.
• “Above” does not include a total that merely equals the line, unless that rung’s wording says otherwise. The published Hormuz language uses “above.”

Buying two rungs is not diversification across two stories. The higher rung pays only in a subset of the weeks that pay the lower rung. Its price should be lower. If the ask on “above 25” is not below the ask on “above 15,” check the spread before you invent a theory about the strait. Stale tail prices are common on far rungs.

A cents price is still a price on that rung alone. The payout arithmetic is in what 60 cents means. It does not become a forecast of the exact ship count.

Tuesday morning is part of the trade

The counting week ends Sunday. PortWatch’s weekly update, as described in the contract notes and in Prediction Scout’s check of settled weeks, is Tuesday at 9 a.m. Eastern. Until that release, the last one or two days can be missing. A market that settles “no earlier than” that hour is telling you the capital stays in the contract after the ships have already sailed.

Prediction Scout re-added PortWatch’s current daily values for settled weeks since April 20, 2026, and found that 41 of 63 settlements matched the totals visible later. The misses are the point of the rule: the contract uses the data available under its own timing, and later revisions do not automatically reopen it. If you need the dispute path when a source is revised, start with settlement rules.

A ceasefire market is a different event

Polymarket has been trading large contracts on whether a U.S.–Iran or Israel–Iran ceasefire continues through a named date. Those contracts name a political condition and a deadline. They do not name PortWatch, and they do not pay $1 because a weekly ship count cleared 15.

The two can move together. They do not have to. Traffic can rise during a ceasefire, fall during a ceasefire, or move because of insurance, schedules, or canal conditions somewhere else. Kalshi also lists separate weekly traffic markets for Hormuz, Suez, Bab el-Mandeb, and Panama. A headline about one waterway is not an input you can paste into all four.

This guide is only about how to read a published statistical contract. It is not a view on the conflict, and it is not advice about shipping, policy, or anything operational.

A checklist for the November 2–8 ladder

1. Confirm the week. November 2 through November 8 is not the week that just ended on November 1.
2. Read the rung. “Above 15” can be a heavy favorite while “above 30” is a tail. Both descriptions can be true.
3. Confirm the source is IMF PortWatch and the unit is transit calls, summed across the seven days.
4. Note the Tuesday 9 a.m. Eastern floor on resolution, and that later data revisions may not count.
5. Do not import a ceasefire price, a Suez price, or a news count of “ships waiting” unless the rule says to.
6. Use the executable ask. A wide no-bid on a far rung is not a cheap probability.

Frequently asked questions

What does a Hormuz prediction market count? Kalshi’s weekly contracts count transit calls in IMF PortWatch. One transit call is one detected ship passage. The week is the sum of the daily counts.

Can more than one threshold pay? Yes. The rungs are nested. A total of 26 makes every line below 26 able to resolve Yes. This is not a one-winner board.

When do the weekly markets settle? The published rule says no earlier than 9 a.m. Eastern on the Tuesday after the Monday-to-Sunday week, once the data are complete.

Is this the same as a ceasefire contract? No. Traffic pays on a ship-count dataset. A ceasefire contract pays on the condition in its own rule. One can be Yes while the other is No.

Sources and methodology

Contract structure, the PortWatch source, the Monday-to-Sunday sum, the “above” lines, and the Tuesday 9 a.m. Eastern timing were checked against Kalshi’s November 2–8 market and Prediction Scout’s November 1 comparison of settled chokepoint weeks with PortWatch. The dataset home is IMF PortWatch. No ship-count forecast is made here.