We are starting a monthly report series
At GEO Meter, we use our proprietary observation infrastructure to analyze and publish the citation patterns of ChatGPT / Claude / Gemini every month. As the first installment, we share the patterns confirmed in initial observations through May 2026 and how to interpret them.
This report aims to:
- Track AI-by-AI differences in citation behavior on a monthly basis (behavior changes over time)
- Share trends confirmed in early observations with readers
- Provide decision material for marketing leaders and implementation owners on "what to improve next"
The numbers behind the observations
- Observation period: 2026-04-22 to 2026-05-28
- Number of observed Topics: 30 (25 for the tax accountant industry ranking + existing Topics)
- Total citation sources: 6,297
- Number of citation queries: 164
- Observed AIs: 3 (Claude / ChatGPT / Gemini)
- Observation query language: Japanese (audience_lang=ja)
Cross-industry statistical aggregation will be published once we have accumulated more observations in subsequent months. In this article, we focus on patterns confirmed in one initial ranking (Shibuya × Startup Financing tax accountants).
Observation 1: Gemini citations include many redirect URLs
In the observation of the
Shibuya × Startup Financing Tax Accountant Ranking,
vertexaisearch.cloud.google.com (Google's internal AI search redirect URL)
was the most frequent citation source domain, at 333 instances (out of 725 total citation sources).
This is because Gemini presents URLs in its responses as intermediary URLs rather
than as the actual domains. When selecting a GEO tool, "whether vertexaisearch
appears high in Gemini's citation sources" is an effective evaluation criterion.
GEO Meter implements logic that converts redirect URLs back to actual domains,
so the original citation source is correctly identified.
Observation 2: 4 of the Top 5 firms are cited across all 3 AIs
Looking at which AIs mentioned the Top 5 firms in this ranking, we see:
| Rank | Firm Name | Cited By |
|---|---|---|
| 1 | 蔵田経営会計事務所 (Kurata Management Accounting Office) | ChatGPT / Claude / Gemini |
| 2 | アップビレッジ経営会計事務所 (Up Village Management Accounting Office) | ChatGPT / Claude / Gemini |
| 3 | サン共同税理士法人 (San Kyodo Tax Accountant Corporation) | Claude / Gemini |
| 4 | 畑間税理士事務所 (Hatama Tax Accountant Office) | ChatGPT / Claude / Gemini |
| 5 | 渋谷融資サポートオフィス (Shibuya Financing Support Office) | ChatGPT / Claude / Gemini |
4 of the Top 5 were cited across all 3 AIs. While this is an observation from a single ranking only, it suggests that firms seen as "strong in AI search" tend to be evaluated across the board rather than favored by a specific AI. Whether this trend holds across other industries and Topics will be shared in subsequent months as we accumulate more observations.
Observation 3: Presence of llms.txt has a large impact on citation rate
In a smoke analysis we ran internally at GEO Meter, covering 2 Topics × 20 domains,
we observed a +20 to +30pp gap in llms.txt adoption rate between the top
and bottom AI citation cohorts.
This is a small-scale analysis, but the trend that the top cohort consistently
maintains llms.txt is strong, and we position it as the highest-priority GEO action.
For implementation, please see the llms.txt Complete Implementation Guide.
Observation 4: Behavioral patterns by AI engine
Differences in behavior by AI engine confirmed in initial observations are below. Detailed quantification will follow in subsequent months of continued observation.
- ChatGPT: Frequently produces list-style candidate enumerations like "Top 10 recommended XX"
- Claude: Many citations are structured around web search results, giving sites with well-maintained Schema.org an advantage
- Gemini: Mainly presents redirect URLs, requiring GEO tools to implement logic that converts these back to actual domains
Per-AI optimization based on these differences is also explained in the Complete Guide to AI Platform Optimization.
Publication plan from next month onward
We plan to continue the monthly analysis with the following structure:
- Cross-industry statistical aggregation: Published once we have enough Topics / rankings
- Changes in per-AI behavior: Tracking algorithm and citation policy updates
- Industry deep dives: Tax accountants / lawyers / clinics, etc. (the focus rotates each month)
- Improvement hints: The next moves to make, derived from the data
Industry-specific GEO observation rankings will be published in sequence. If you want to know your business's AI search visibility, please try the free diagnostic.
→ Try the free diagnostic → Tax Accountant Ranking (Shibuya × Startup Financing)