{"id":2110,"slug":"caveats-market-difficulty-vendor-quarantine","title":"Caveats — vendor quarantine and the correlational-vs-causal divide","kind":"reference","scope":"business","status":"current","audiences":["kevin","candid-team"],"topics":["incumbent-authority-accumulation","review-revenue-causal-evidence"],"reference_body":"**Honest gaps:**\n\n1. **Correlation vs causation pervades this field.** Almost all ranking-factor evidence (links, age, brand) is correlational. The rare causal exceptions: review-impact studies (Luca regression-discontinuity, Spiegel conversion experiments); antitrust-confirmed NavBoost existence.\n2. **Survivorship/selection bias is rampant.** SEO case studies and \"we outranked a 2015 competitor in 8 months\" stories feature only winners. The Ahrefs 1.74% figure is the closest thing to a base rate and it is sobering.\n3. **Vendor incentive bias.** Large share of all published data in this domain comes from companies selling SEO tools or services. Numbers quarantined accordingly.\n4. **Ground is shifting fast.** AI Overviews, AI Mode, and zero-click behavior are changing quarter to quarter; any difficulty model must be re-baselined regularly. Google's own claims that AI Overviews keep click volume \"relatively stable\" conflict with independent publisher data and Pew — unresolved dispute.\n5. **Most data is US-centric.** Whitespark (Edmonton, Alberta) and BrightLocal provide some Canadian-relevant local-search grounding, but vertical- and country-specific difficulty can differ materially.\n6. **Tool numbers are not measurements.** KD / DA / DR are proprietary estimates, not Google signals; Google does not use them.\n\n**Quarantined vendor sources:** Ahrefs, Semrush, Moz, SE Ranking, Keywords Everywhere, SpyFu, Serpstat, Mangools, Ubersuggest, Whitespark, BrightLocal, Uberall, Sterling Sky, GatherUp, Seer Interactive, NP Digital, SparkToro.\n\n**Non-vendor / higher-trust sources used:** Pew Research Center (Pew 2025 browsing-data study), Michael Luca / Harvard Business School (peer-reviewed-grade Yelp study), Northwestern Spiegel Research Center (academic), US DOJ v. Google trial testimony, Google's own documentation and spokespeople (Mueller, Ohye, Nayak), and peer-reviewed review-impact literature.","rationale_body":null,"metadata":null,"links":{"outgoing":[],"incoming":[{"slug":"research-brief-smb-widget-market-difficulty-june-2026","title":"Research brief: SMB widget market difficulty — six ranked factors (June 2026)","kind":"reference","scope":"business","link_type":"relates-to"}]},"created_at":"2026-06-23T19:16:04.258Z","updated_at":"2026-06-23T19:16:04.258Z"}