Caveats — vendor quarantine for tier-mapping evidence

Quarantined vendor sources (commercial incentive flagged — used directionally only):

• Whitespark (Edmonton, Alberta) — sells local-SEO tools/services. Source of GBP weighting and ranking-factor survey.
• BrightLocal — sells local SEO/citation/review tools. Source of consumer review survey.
• Ahrefs / Semrush / Moz — SEO SaaS. Ranking, citation, timeline statistics. Ahrefs' 1.7% figure cuts against own incentive (more credible).
• Local Falcon, ReplyOnTheFly, BizIQ, SOCi, Schema App, AI-SEO vendors (AirOps, Stridec, CXL) — sell the exact service described.
• Web-design agencies — repackage academic credibility / 27%-no-website stats with incentive to sell websites.

Non-vendor / higher-trust sources used: Google Search Central / Google for Developers, web.dev, Google/SOASTA research, HTTP Archive Web Almanac, schema.org, peer-reviewed journals (Lindgaard 2006; Robins & Holmes 2008), Harvard Business School (Luca WP 12-016), Statistics Canada / ISED for Canadian baselines.