A SISTRIX analysis of 3.8 million German-language ChatGPT responses found that citation patterns changed after ChatGPT began implementing GPT-5.5.
THE analysispublished by Johannes Beus, founder of SISTRIX, tracked 38 daily samples of 100,000 ChatGPT responses. SISTRIX compared quotes from the four days before the change with those from the four days after.
The company describes the event as a “ChatGPT core update,” comparing it to how Google core updates change search rankings. SISTRIX also notes that the data shows a correlation, not proof that the model change caused the movement in citations.
For the sake of transparency, SISTRIX sells Prompt Tracking, the product used to collect data for analysis.
What the data shows
On a typical day during the tracking period, citation patterns ranged from 1 to 2 percent. During the model ID change on May 22 and 23, this figure increased to 47%.
The average number of sources cited per response also decreased, from 30.9 before the change to 28.4 after.
SISTRIX’s comparison of 800,000 responses across the before and after change windows shows a trend between winners and losers.
Winners
Reddit saw the largest absolute gain, adding 7,007 quotes per 10,000 replies, a 59% increase. Reddit was already the most cited domain before the change.
The major German publishers have made progress in all areas. Welt.de grew by 99%, faz.net by 124% and bid.de by 83%. German streaming and sports platforms also made progress. Dazn.com grew by 383%, sky.de by 157% and kicker.de by 357%.
Specialized tools and sources of acquired knowledge as well. Mapbox.com and openstreetmap.org each increased by 83%, and justwatch.com by 624%.
Losers
International aggregation platforms saw the largest declines. In fact, they fell by 47%, Tripadvisor by 53% and Glassdoor by 37 to 52% in the national versions. Expedia and Rome2rio each fell 60%.
Global technology platforms have also lost ground. YouTube fell 18%, Wikipedia fell 14% and Google.com fell 22%. Facebook and LinkedIn each fell about 20%.
German career and comparison portals also list the visibility, Kununu fell by 46%.
The industry model
The analysis reveals three winning categories in the German data: German media, Reddit and specialist tools all won. Conversely, three losing categories included: international aggregators, global technology platforms and German career portals.
Beus interprets the model as a localization. For German-language queries, ChatGPT responses contained more German sources after the change, including established publishers and German service brands.
According to SISTRIX, the data does not allow us to determine whether this was the objective of the model.
Reddit is the exception. Although it is predominantly English-speaking, it has continued to gain ground. This suggests that user-generated discussions on all topics continue to be considered highly relevant.
Why it matters
The results add to growing evidence that ChatGPT’s citation behavior changes with each model. SEJ covered Resoneo data showing that the GPT-5.3 transition reduced the domains cited per response. Separate analysis showed that ChatGPT’s default and premium models already produce different citation patterns.
The SISTRIX data now shows how citation patterns changed around a visible change in model version in a large sample.
Looking to the future
The analysis only covers the German market. SISTRIX notes that similar trends have been observed in other markets, but has not published this data. The company says it will continue to track citation patterns through its Prompt Tracking product.
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