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Planning fallacy and deadline markets

In 1979, psychologists Daniel Kahneman and Amos Tversky described the planning fallacy: people tend to underestimate how long their own projects will take, even when they know similar projects ran late. The bias shows up everywhere — construction, software, legislation, corporate deals, and product launches. In prediction markets, it shows up in by-date contracts.

Why by-date markets are exposed

A large share of event contracts ask whether something happens before a deadline: a product ships, a bill passes, a deal closes, a mission launches, a treaty is signed. Public timelines usually come from the people doing the work, who have every incentive to sound confident. Readers who anchor on the announced date inherit the optimism. Our by-date deadline markets guide explains the contract mechanics.

Inside view vs outside view

Kahneman distinguished two ways of forecasting:

• Inside view: Reason from the specifics of this project — its plan, team, and stated milestones.
• Outside view: Ask how long similar projects actually took, then adjust.

The outside view tends to be more accurate for timing questions. Base rates for slippage can be large: software releases, infrastructure projects, and legislative calendars often miss their first targets. See base rates and reference classes.

Where timelines slip

Common reasons:

• Dependencies: One delayed approval or component pushes everything back.
• Regulatory steps: Reviews, comment periods, or court challenges add time.
• Negotiations: Deals and agreements stall over final terms.
• Testing: Launches and releases wait for problems to be fixed.

Our guides on tech product launch dates and space launch milestones cover sector-specific patterns.

The status quo advantage

When a deadline passes without the event, a by-date market usually settles No. That gives No a structural advantage in many timing questions — something happens only if every step completes in time. Read status quo and nothing-happens pricing.

Time decay

As a deadline approaches without progress, a Yes price should generally fall. Readers affected by the planning fallacy may hold on to optimistic estimates longer than the evidence supports. See time decay into event resolution.

The opposite error

The planning fallacy is not a rule that everything runs late. Some events are scheduled by law, such as elections and data releases, and happen on time almost always. Others are under the control of a single decision-maker who can act quickly. Apply the outside view to the right reference class.

A worked example

A company says a new product will launch by the end of the quarter. A market on launch by the quarter's end trades at 80 cents (illustrative — verify live). A reader checks the company's record: of its last several announced launch windows, how many were met? If roughly half slipped, 80% may look optimistic — unless there is concrete evidence, such as regulatory clearance or shipping notices, that the launch is on track.

Before you act on a price

• Read the full title and rules, including the named settlement source, the threshold, and the time zone.
• Convert the Yes and No prices to implied probabilities with the implied probability tool and note the gap between them.
• Account for fees and spread — the fee drag tool uses assumptions only, so verify the live schedule on the venue.
• Write your own probability range and the evidence behind it before comparing it with the crowd.
• Check related and near-duplicate markets for consistency; prices on this page are illustrative — verify live cents on the operator.

The bottom line

ChanceWire guides, hubs, and tools are orientation, not order entry. We do not sell picks, invent partner bonuses, or describe any market as a sure thing. Confirm your age, location, and product eligibility on the operator itself — we will never suggest location spoofing or access workarounds. If the definitions are still unclear after reading the rules, watching without trading is a perfectly reasonable outcome. Event contracts carry substantial risk of loss.