Question and design
What share of URLs cited in the Absence Index release 2026-09 carry visible optimization signals, and how does that share differ by engine and software category? This is a descriptive secondary-data study, with no directional hypothesis and no causal test of whether a signal produces a citation.

Source and prior knowledge
Use the published answers-2026-09.jsonl and release-2026-09.json attached to version DOI 10.5281/zenodo.22907695, with their published checksums. These answers were already collected and made public before this registration. Published aggregate counts and the comparison paper have been read. No new study results, host classification totals or page-signal shares have been computed. All three research-section plans must be registered before analysis begins.

Units and inclusion
Include every explicit citation URL in the archived answers. Retain engine, category, question, repeat, capture date and citation order for every occurrence. Deduplicate the analysis units by exact URL, preserving scheme, path, query and fragment in the unit identifier. Preserve a separate mapping to the requested resource URL. A URL contributes once to each engine or category stratum in which it occurs. Report target and control questions separately as well as the combined archive; do not treat a missing answer or an answer without a citation as a URL with no optimization. Retain excluded answer rows in a separate audit, but omit their citation URLs from the primary eligible-answer analysis unless the same URL also appears in an eligible answer. Give any all-record sensitivity analysis a separate label. Preserve extraction exclusions and reasons. Report any archival mismatch before continuing.

Collection
Retrieve each resource once and cache the result. Observe robots.txt and a maximum of one request per second per host, including redirects and host-root files. Use BroadcastwellResearchBot/1.0 (+https://docs.broadcastwell.com/research/). Do not fetch restricted client domains. Record requested and final URL, fetch date, status, content type, redirect chain and time to first byte. Record robots exclusions, blocked responses, 4xx, 5xx, timeout, non-HTML and other failures separately. A failed fetch is never evidence that a page is not optimized. Do not evade access controls. Keep raw HTML out of the public dataset.

Signals and classification
Record non-empty title and meta description; canonical link; Open Graph tags; viewport meta; JSON-LD or microdata and reported schema types; SEO plugin signatures, including Yoast, Rank Math, All in One SEO and SEOPress; analytics and advertising signatures; HTTPS; host-root robots.txt, sitemap and llms.txt; and time to first byte. Distinguish absent, present and unknown for host files. Publish exact signal rules and a host evidence table. Freeze any news-domain list and additional signature dictionary before aggregating outcomes; additions after inspecting results are exploratory and reported as deviations.
Apply this precedence to successfully fetched HTML: (1) Wikipedia and sister projects: definitely not optimized, a stipulated class rather than a quality judgment; (2) an SEO plugin, structured data, a documented news-domain classification or an advertising signature: definitely optimized; (3) otherwise, a missing title or missing meta description: probably not optimized, overriding weak positive signals; (4) otherwise at least one weak signal: probably optimized. Weak signals are analytics, HTTPS, canonical, viewport, Open Graph, sitemap, explicit SEO hints in robots.txt, or time to first byte below three seconds. Any residual page is unclassified, not forced into a negative class. The time-to-first-byte threshold is our adaptation; Lewandowski et al. used page loading time below three seconds. A public rule table will distinguish this adaptation and the expanded structured-data rule from the paper's fitted decision tree.

Statistics and finding rule
For each class report numerator, eligible URL base, percentage and two-sided Wilson 95% interval overall, per engine and per category. Report unclassified and failed units with their own bases. Give citation-order results only when the archive provides order; do not infer answer rank from a host list. Separately report Wikipedia share, llms.txt presence and schema-type frequencies with explicit denominators and unknowns. Strata overlap and repeat answers are dependent; Wilson intervals describe uncertainty conditional on this archive and are not population confidence claims. No significance tests or claims of representativeness. A finding is a reproducible descriptive count or share supported by the released classification CSV, including a null or low observed share.

Comparison and limits
Compare only descriptively with Figure 1 of Lewandowski, Suenkler and Yagci (2021), DOI 10.1145/3447535.3462479: 59.0% definitely optimized, 29.0% probably optimized and 12.0% (probably) not optimized among 256,853 Google result URLs. State method differences first: German Google query sets in 2020 versus archived B2B software questions across five answer engines in September 2026; later fetch date; different signal and classification implementation. Cite the paper's chart rather than conflicting prose. Its 27% figure concerns the position of its Wikipedia results, not Wikipedia's share of all first-position results. A cited URL is not proof of the answer's source of truth, a fetched page may have changed since the answer, and this question set is not a representative sample of buyer searches. Publish code, classification CSVs, failures and deviations; do not claim control of AI answers.