# Citation half-life

> Citation half-life measures how quickly unchanged content loses visibility in AI answers — around 4.5 weeks on average. Why freshness matters for AI visibility.

Synonyms: citation decay, half-life of AI citations

The term transfers half-life from physics to AI answers: how long until an unchanged piece of content is cited only half as often? A study by Scrunch and Stacker (2026) analysed more than three million citation events across eight industries over 26 weeks — finding a median half-life of roughly 4.5 weeks, ranging from about 3.4 weeks (ChatGPT) to almost 6 weeks (Perplexity) depending on the AI system.

The reason: AI systems visibly prefer fresh sources. Older content is not wrong — newer content simply crowds it out. According to the same analysis, sites that update regularly are cited about three times as often (3.2×) as sites left unchanged.

For businesses this suggests a simple rhythm: review and visibly maintain core facts such as opening hours, services and prices on a regular basis. AI visibility is not a one-off task but ongoing care — and citation half-life makes that measurable for the first time.

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Source: https://btlabs.dev/en/glossary/citation-half-life
Last-Modified: 2026-08-03T10:39:27.064Z
Languages: [de](https://btlabs.dev/llms/de/glossary/zitations-halbwertszeit) · [it](https://btlabs.dev/llms/it/glossary/emivita-delle-citazioni)
See also: [llms.txt](https://btlabs.dev/llms.txt) · [ai.txt (Policy)](https://btlabs.dev/ai.txt) · [identity.json](https://btlabs.dev/identity.json)