How Often Does a Shutdown Threat Actually Become a Shutdown?

Congress routinely misses the October 1 appropriations deadline. An actual shutdown at that specific deadline is much rarer.

01The question

The Kalshi contract asks whether the federal government will be at least partially shut down because of a lapse in appropriations at 10:00 a.m. Eastern on October 1, 2026. The hour matters more than the headline suggests. A lapse that begins on October 15 pays nothing. A brief technical gap where agencies keep working normally pays nothing. What settles YES is a formal OMB directive to execute shutdown plans in effect at that hour, or an OPM operating status showing agencies dark because the money ran out.

02What shutdown history actually says

There have been 50 October 1 deadlines since fiscal year 1977. Congress enacted all twelve appropriations bills on time in four of them. Missing the deadline is the normal condition of the institution, not a crisis.

Missing it and shutting down are separate events. Of the 46 misses, only 8 produced a funding gap at the October 1 boundary at all. In the other 38, a continuing resolution was already law before the clock ran out.

Missing the appropriations deadline is normal. Missing it without a continuing resolution is not.

The coding of those last few cases is worth doing carefully, because the whole forecast rests on it. Of the 8 gaps, four happened before 1980, when agencies simply kept working through a lapse and the modern shutdown did not legally exist. One more, in October 1984, ended without furloughs because a bill had passed and everyone knew the signature was coming.

That leaves October 1982, October 2013, and October 2025. The 1982 case is marginal: it ran a single day across a Friday into a Saturday, furloughs were not anticipated, and it is unclear whether employees were even told to stay home. Strict coding counts only the two real, extended shutdowns, which gives 2 of 50, or about 4 percent. Inclusive coding adds 1982 and gives 3 of 50, or about 6 percent.

Neither number is the one used here. Restrict the record to the high-brinkmanship years since 2010, where funding fights became a routine instrument rather than an occasional accident, and the rate rises to roughly 12 percent. That is the base rate this forecast starts from, and it is why the estimate does not sit down at four to six.

03Why most funding fights do not become shutdowns

The escape hatch is cheap. A continuing resolution extends existing funding at existing levels and settles nothing, which is precisely why it passes. Voting for one requires nobody to abandon a position.

Watch what leadership does rather than what anyone says. In September 2024, Speaker Johnson brought a stopgap carrying a contested election-law provision to the floor and lost, 202 to 220. A week later he dropped the provision and passed a clean bill 341 to 82 using minority votes. In September 2023, Kevin McCarthy's own bill failed on the 29th. He passed a clean 45-day extension the next day using minority votes, and lost the speakership for it three days after that. The faction demand was real in both cases. Leadership went around it in both cases.

04Where Congress is today

This year is unusual, and the direction of the unusualness favors NO.

• The House passed a stopgap on July 21, running to December 4.
• The Senate passed its own stopgap on August 8 by 90 votes to 6, running to December 11.
• The two bills differ and still need reconciliation. Neither chamber has voted on the other's text.
• The House margin is roughly 218 to 215, so a handful of defections can deny a rule for floor debate.
• The Senate does not return until September 14, leaving roughly twelve session days.
• The disputes behind the fiscal 2026 lapses are no longer active in the same form. Immigration enforcement funding was settled separately in June for three years, and the health care subsidy fight expired at the end of 2025.
• A short bridge extension of a few days remains available and would resolve this contract NO.

Nothing resembling that second line has been true five weeks out in any year that ended in an October 1 shutdown. The open items are narrower than the headline suggests: the Senate version blocks a proposed rule on federal grants, closes a route for transferring money to Border Patrol, and delays a ban on THC-infused hemp products scheduled for November 12. The chair of the House Freedom Caucus is fighting the hemp piece. He has not said he will vote against the bill.

05What would have to break

A shutdown at that specific hour is not one failure. It is a chain, and every link has to give way.

1. The House and Senate fail to reconcile their two stopgaps.
2. Leadership cannot find bipartisan votes for a compromise, and cannot pass a short bridge extension either.
3. The President does not sign an available compromise.
4. Shutdown procedures are actually in force at 10:00 a.m. Eastern on October 1.

PastBehavior thinks that chain completes about 12% of the time in the current setup.

The last link deserves attention on its own. A bridge of a few days is the cheapest thing Congress can pass, it has precedent in 1984 and 1987, and it settles this contract NO even if the underlying fight runs on for weeks afterward.

06Where PastBehavior and the market disagree

There is no meaningful disagreement here in either direction. A two-point gap sits inside the noise of a one-cent spread.

07The forecast

Twelve percent, with a defensible range of eight to twenty.

The case for a shutdown is real and it is the reason the estimate does not fall toward the unconditional four to six percent. The House margin is extremely narrow, and a few defections can kill a rule for floor debate. The Senate calendar is compressed, with about twelve working days after September 14 and a chamber that moves at the speed of its most obstinate member. December 2018 proved that agreement between both chambers does not guarantee a presidential signature: the Senate passed a clean stopgap by voice vote, the President reversed course, and 34 days of shutdown followed. And this Congress has tolerated several funding lapses in the past year, including the two longest on record, so it earns less benefit of the doubt than the long historical record alone would give it.

What keeps the number from going higher is that each of those recent lapses ran through one chamber's minority withholding votes over a named substantive demand. Those senators have already voted for this bill, ninety to six, after getting concessions written into it.

No paper position is opened on a PASS forecast.

08What would change the view

1. A scheduled House floor vote on the Senate stopgap moves PastBehavior toward 5 to 8 percent.
2. No House floor vote on any continuing resolution by September 20 moves the probability toward 22 to 25 percent.
3. A presidential demand to attach a major policy condition, or a new funding-related political shock, moves the probability above 40 percent.

09What this experiment is testing

PastBehavior is testing whether historical patterns can produce forecasts that can be written down, compared against a market, and scored after resolution. A PASS is part of that record too.

This is Prediction Markets No. 005.