Here's what the evidence actually supports.
The Three Variables Google Actually Uses
The Content Warehouse API leak revealed three specific attributes that confirm Google quantifies topical authority at the site level:
site2vecEmbeddingEncoded is a compressed vector embedding representing an entire site's thematic identity as a mathematical pattern. Google creates a single numeric fingerprint of what your site is "about."
siteFocusScore measures how dedicated a site is to a specific topic. High scores indicate specialist sites; low scores indicate generalist or unfocused properties.
siteRadius measures how much individual pages deviate from the site's central theme. Low siteRadius means tight topical alignment. High siteRadius means pages that don't belong.
These aren't abstract ranking concepts. They're documented attributes in Google's internal API, complete with data types and module references. A site demonstrates topical authority by achieving a high siteFocusScore while keeping siteRadius low across its important content.
Topical focus and quality are independent variables. As the Hobo-Web analysis points out, The New York Times has exceptional quality but low topical focus as a generalist publication. A niche site about aquarium filtration could have a perfect siteFocusScore and terrible content. Google evaluates both, separately.
Does It Actually Move Rankings?
The theoretical framework is useful. Does topical authority actually move rankings?
Surfer SEO's analysis of 253,800 search results found that page-level topical authority is the strongest on-page ranking factor, outperforming even domain traffic volume. That's a significant sample size, and the finding was consistent across verticals. Their survey data adds context: 88% of SEOs rate topical authority as "very important" to their strategy.
Graphite's controlled study took a different approach, analyzing 332 URLs across 12 domains. They segmented content into three buckets by topical authority score and tracked time-to-visibility. High-authority content reached first clicks substantially faster than low-authority content. The study used real indexing and click data, not just correlations.
OnCrawl published case studies showing a 1,100% traffic increase on Interingilizce.com (10,000 to 200,000 monthly clicks in 145 days) using a pure topical authority strategy. The study deliberately excluded pagespeed optimization, technical SEO, brand building, and on-page SEO elements. A second project, GetWordly.com, went from zero to 330,000 monthly clicks in six months using the same approach.
Our read: the OnCrawl case studies are dramatic but should be taken with context. These were relatively low-competition markets (Turkish and Azerbaijani language content), and the results may not generalize to competitive English-language SERPs. The Surfer and Graphite studies are more methodologically rigorous for drawing broad conclusions.
Building Clusters That Actually Work
The evidence points to a clear implementation model: hub-and-spoke content clusters with intentional internal linking.
SearchAtlas's analysis of 400+ SEO campaigns puts numbers on what "realistic" means: 25–30 high-quality, interlinked articles within a single content cluster, with sites achieving that threshold seeing a 40–70% increase in keyword rankings within 3–6 months. Building a cluster (pillar page plus supporting articles) costs roughly $1,000–$3,000 in content investment.
For comparison, they estimate improving domain authority by a single point costs $500–$2,000 in competitive industries, and meaningful DA gains take 12–24+ months.
Search Engine Land's topic clusters guide cites HireGrowth's 2025 analysis showing clustered content drives about 30% more organic traffic and holds rankings 2.5x longer than standalone pieces. One documented rollout of hub-and-spoke architecture drove a 53% lift in three weeks.
The internal linking piece matters more than most people realize. It's not just about having the content — it's about connecting it so Google can trace the topical relationships. Two-way links between pillar and supporting pages are standard practice, but anchor text diversity also plays a role.
Four Ways to Waste Your Budget
More content does not automatically mean more authority. This is the single most common mistake, and the API leak data explains why: pages that deviate from your core theme increase your siteRadius, which hurts your siteFocusScore.
Specific failure modes the research identifies:
Keyword cannibalization. Multiple pages targeting the same intent compete against each other instead of reinforcing authority. A cluster needs clear intent differentiation between supporting pages.
Topic drift. Publishing content that's adjacent-but-not-really to your core expertise. A B2B SaaS blog publishing general business advice pieces is adding noise, not authority. Every page that doesn't fit tightens or loosens that siteRadius number.
Neglecting the links. You can have 30 excellent articles on a topic, but if they're not interlinked with clear topical relationships, Google's clustering signals don't fire the same way. The content exists; the authority signal doesn't.
Confusing volume with depth. Ten thin articles covering surface-level subtopics will lose to five thorough articles that genuinely exhaust their subject. Successful pillar pages typically run 2,000+ words, balancing thorough coverage with readability.
The February 2026 Update Changed the Calculus
Google's February 2026 core update strengthened topical authority as a ranking signal specifically. Early analysis suggests the update penalizes thin AI-generated content and rewards sites demonstrating genuine topical depth.
The update evaluates expertise at a granular level. Google's systems identify expertise on a topic-by-topic basis, meaning authority is assessed per subject area rather than as a blanket domain-level signal. A technology site with deep coverage of cloud infrastructure doesn't automatically get credit for articles about consumer electronics.
This aligns with the direction Google's been heading since adding "Experience" to E-A-T in late 2022. The 2025 Quality Rater Guidelines extended E-E-A-T requirements beyond YMYL topics to virtually all competitive queries. Trust remains the most weighted factor, but topical expertise is now the clearest differentiator between sites that hold rankings and sites that don't.
The practical implication: topical authority is becoming less of a nice-to-have content strategy and more of a structural requirement for competing in organic search. Sites that built depth early are pulling ahead. Sites that spread thin across too many topics are feeling the squeeze.
This isn't a quick fix. The data consistently shows 3–6 months for meaningful results, real investment in content quality, and disciplined focus on what you're actually expert in. The sites winning with topical authority aren't the ones that published the most. They're the ones that published the most coherent body of work on topics they genuinely own.