gbanyan
ef0e417257
Opus 4.7 max-effort round-12 on v3.12 found 1 MAJOR + 7 MINOR residues;
codex gpt-5.5 xhigh round-13 cross-verified 11/11 RESOLVED and caught
one additional cosine-P95 ambiguity Opus missed (methodology L255).
Total 12 text-only edits across 5 files.
MAJOR M1 - Cosine P95→P7.5 terminology residue at two sites that cite
the v3.12-corrected Section III-L but still wrote "P95" (self-
contradiction). Fix: methodology L165 and results L247 both restated
as "whole-sample Firm A P7.5 heuristic" with the 92.5%/7.5%
complement spelled out.
MINOR findings and fixes:
- m1 Big-4 scope slip: methodology III-H(b) L166 and results IV-H.2
L311 said "every Big-4 auditor-year" but IV-H.2 ranking actually
pools all 4,629 auditor-years across Big-4 and Non-Big-4. Both
sites now say "every auditor-year ... across all firms."
- m2 178 vs 180 Firm A CPA breakdown: intro L54 and conclusion L21
now add "of 180 registered CPAs; 178 after excluding two with
disambiguation ties, Section IV-G.2" parenthetical to avoid the
misleading 180−171=9 reading.
- m3 IV-H.1 A2 citation: results L286 now explicitly invokes the
A2 within-year label-uniformity convention (Section III-G) when
reading the left-tail share as a partner-level "minority of hand-
signers."
- m4 IV-F L177 cross-ref / fold distinction: corrected Section III-H
→ Section III-L anchor, and added explicit note that the 0.95
heuristic is a whole-sample anchor while Table XI thresholds are
calibration-fold-derived (cosine P5 = 0.9407).
- m5 Table XVI (30,222) vs Table XVII (30,226) Firm A count gap:
results L406 now explains the 4-report difference (XVI restricts
to both-signers-Firm-A single-firm two-signer reports; XVII counts
at-least-one-Firm-A signer under the 84,386-document cohort).
- m6 Methodology L156 "four independent quantitative analyses"
actually enumerated 6 items: rephrased as "three primary
independent quantitative analyses plus a fourth strand comprising
three complementary checks."
- m7 Abstract "cluster into three groups" restored the "smoothly-
mixed" qualifier to match Discussion V-B and Conclusion L17.
- Codex-caught residue at methodology L255 ("Median, 1st percentile,
and 95th percentile of signature-level cosine/dHash distributions")
grammatically applied P95 to cosine too. Rewrote as
"cosine median, P1, and P5 (lower-tail) and dHash_indep median
and P95 (upper-tail)" matching Table XI L233 exactly.
No re-computation. All tables (IV-XVIII) and Appendix A numbers
unchanged. Abstract at 249/250 words after smoothly-mixed qualifier.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2.1 KiB
Abstract
Regulations require Certified Public Accountants (CPAs) to attest to each audit report by affixing a signature. Digitization makes reusing a stored signature image across reports trivial---through administrative stamping or firm-level electronic signing---potentially undermining individualized attestation. Unlike forgery, non-hand-signed reproduction reuses the legitimate signer's own stored image, making it visually invisible to report users and infeasible to audit at scale manually. We present a pipeline integrating a Vision-Language Model for signature-page identification, YOLOv11 for signature detection, and ResNet-50 for feature extraction, followed by dual-descriptor verification combining cosine similarity and difference hashing. For threshold determination we apply two estimators---kernel-density antimode with a Hartigan unimodality test and an EM-fitted Beta mixture with a logit-Gaussian robustness check---plus a Burgstahler-Dichev/McCrary density-smoothness diagnostic, at the signature and accountant levels. Applied to 90,282 audit reports filed in Taiwan over 2013-2023 (182,328 signatures from 758 CPAs), the methods reveal a level asymmetry: signature-level similarity is a continuous quality spectrum that no two-component mixture separates, while accountant-level aggregates cluster into three smoothly-mixed groups with the antimode and two mixture estimators converging within $\sim$0.006 at cosine \approx 0.975. A major Big-4 firm is used as a replication-dominated (not pure) calibration anchor, with visual inspection and accountant-level mixture evidence supporting majority non-hand-signing alongside within-firm heterogeneity consistent with a minority of hand-signers; capture rates on both 70/30 calibration and held-out folds are reported with Wilson 95% intervals to make fold-level variance visible. Validation against 310 byte-identical positives and a $\sim$50,000-pair inter-CPA negative anchor yields FAR \leq 0.001 at all accountant-level thresholds.