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Lindy effect and survival-time estimates for by-date markets

Many event contracts ask how long something will last: whether a ceasefire holds through a month, whether a leader stays in office until a date, whether a record stands through the season. Survival-time reasoning gives a framework for these questions. One popular heuristic is the Lindy effect. This SoftCta guide explains it, along with its limits.

The Lindy effect

The Lindy effect holds that for some things that do not age physically, such as books, technologies, institutions or ideas, the expected remaining lifetime grows with the time already survived. A technology that has been in use for 50 years is, on this view, more likely to be in use in another 50 than one that appeared last year. In survival-analysis terms, it implies a falling hazard rate: the chance of ending in any given period declines as the thing ages. Our guide on hazard rates explains how hazard rates translate into by-date probabilities.

Gott's Copernican estimate

Physicist J. Richard Gott suggested a related rule. If you observe something at a random moment in its existence, there is a 50% chance you are in the middle half of its lifetime. That implies a 50% chance its remaining duration is between one third and three times its current age. It is a rough tool, useful when you know almost nothing else, and it has been applied to questions such as how long a stage show will run.

Where it fails

Survival reasoning goes badly wrong when the hazard rises with age. People, machines and many political arrangements age or wear out. Fixed-term offices have scheduled end dates. A ceasefire may become more fragile as deadlines in its terms approach. In these cases, having lasted longer can mean being closer to the end, not further. Readers should ask whether the thing in question is closer to an idea, which may be Lindy-like, or to a lease, which is not.

Combining with base rates

The better approach usually starts with a reference class: how long have similar ceasefires, coalitions or records lasted historically? Our guide on base rates explains how to choose one. Survival-time heuristics can then adjust that base rate for current age. For things with no history at all, our rule of succession guide covers first-time events.

By-date contracts

A by-date contract asks whether something ends, or happens, before a deadline. Our guide on how by-date markets resolve explains the mechanics. Under a constant hazard, the probability of ending within a window grows smoothly with the window's length. Under a falling hazard, most risk is concentrated early. Under a rising hazard, risk builds as time passes. Matching the hazard shape to the situation changes the price you would consider fair. Our guide on status quo pricing explains why markets often lean towards no change.

A reading habit

• Ask whether the thing ages, wears out or has a scheduled end.
• Use a reference class first, then adjust for how long it has lasted.
• Consider whether the hazard is falling, constant or rising.
• Treat Lindy and Copernican estimates as rough priors, not answers.

Convert prices with the implied probability tool and verify live prices on the venue before reacting to a quote.

Primary sources SoftCta readers open

• Academic literature on survival analysis and hazard functions
• Gott (1993) on Copernican lifetime estimates
• Historical datasets on leader tenure and ceasefire duration
• Reference-class data for the relevant event type

Reading the quote step by step

• Read the full title and rules, including the named settlement source and the time zone.
• Convert the Yes and No prices to implied probabilities and note the gap between them.
• Subtract fees and spread to see the effective price you would actually face.
• Write your own probability range and the evidence behind it, then compare.
• Check related and near-duplicate markets on other venues for consistency.

Closing SoftCta checklist

• Re-read the venue definition in your own words before reacting to a price.
• Convert prices with fee and spread awareness; verify live cents on the operator.
• Prefer primary settlement sources over secondary headlines and social summaries.
• Treat ChanceWire hubs, movers, and tools as orientation — not order entry.
• Confirm age, location, and product eligibility; SoftCta pages will not suggest location spoofing.
• If clarity is incomplete, watching is a complete SoftCta outcome — no pick-selling urgency required.

SoftCta habits

• Write your own probability range before checking the crowd price.
• Prefer dated primary sources over social summaries.
• Compare related markets when a single book looks extreme.
• Size curiosity with fees and depth in mind; substantial risk of loss.