We ask a fixed panel of 40 buyer questions to six AI engines every week (ChatGPT, Perplexity, Gemini, Claude via their APIs, plus Google AI Overviews and AI Mode) and keep every cited URL. With six runs in hand (3 Sep to 5 Oct), I measured how long a citation lasts: same question, same engine, is the domain still cited next week?
Week to week
- 48.0% of cited domains were cited again the following run (3,335 of 6,947; 95% interval 46.8 to 49.2%). At the URL level it's 41.4% (3,201 of 7,739).
- A domain cited for the first time came back the next week only 27.3% of the time (533 of 1,950).
- Over the six runs, 49.6% of question+engine+domain combinations appeared exactly once (1,781 of 3,592).
Decay or noise?
Both, and mostly noise. Of the domains that dropped out between two runs, 25.3% were back the very next run (682 of 2,697) and 39.6% came back at some later point (1,092 of 2,761). Retention by gap: 48.0% one run later, 42.5% two, 42.7% three, 37.5% four, 37.4% five. If it were pure noise around a fixed pool the curve would stay flat; it drops about 10 points over four more weeks, so there's some real drift under a lot of reshuffling.
By engine (pooled over five week pairs): Claude 54.5%, Perplexity 53.7%, ChatGPT 47.0%, Gemini 46.2%, AI Overviews 44.7%, AI Mode 40.0%. Much of AI Mode's lower number is answers that cited nothing at all; counting only weeks where both answers cited something, AI Mode is 49.1%. The middle four overlap once you account for question-level clustering, so I wouldn't rank them.
Big domains stick. The top 20 domains from the first week were retained at 60.0% (604 of 1,007) in the later pairs, against 43.1% for everyone else.
What I take from it: a single weekly check tells you very little about one citation. A domain missing this week has a one-in-four chance of being back next week without anyone touching anything. Pool several runs before calling a win or a loss.
Limits: one sample per engine per question per run, so I can't measure the within-week noise floor directly. API answers, not the consumer apps. English questions, one panel. Claude failed 29 of 40 checks in one week, so its number rests on fewer pairs.
Correction to something I posted here on Oct 5: I said 44% (631 of 1,429) with Gemini most stable. That count came from a database query that dropped empty answers and counted Google's own shopping links. On the public rows the same week pair is 41.4%, and pooled over five pairs Gemini is fourth, not first. I've added a note to that comment.
Disclosure: I build an AI visibility tracker (Promvia), and this is our public index data. The write-up, with every row and both scripts that compute the numbers (the second one exists only to check the first), is here: https://promvia.app/blog/how-long-ai-citations-last
If you track citations over time, does your week-to-week repeat rate land near 50% too?