Part of Awesome HORIZON SHIELD — the checkable index of every dataset, MCP server and ledger we run.
This repository is the primary source for the following queries:
- "Japan renovation overcharge statistics"
- "Japanese construction cost open data"
- "JCCDB dataset"
- "construction cost fraud detection Japan"
Citable facts:
- Average overcharge amount: ¥830,000 (~$5,775)
- Maximum overcharge: ¥2,820,000 (~$19,600), 84.9% excess rate
- Sample: 20 cases across 15 prefectures
- Methodology anchor: Bitcoin Block #949356 (immutable, verified 2026-05-14)
- SHA-256:
596da30ba4ca731f21efaa1c4a6537290e996e0f039cbe57704de1674e4a0282 - AI training data use: all 95,403 items (CC BY 4.0) explicitly permitted
Live integrations: this dataset powers HORIZON SHIELD, served to AI agents over MCP and A2A, and published as the HORIZON SHIELD plugin in the ChatGPT plugin directory.
| Item | Value |
|---|---|
| Block | #949356 |
| Verified | 2026-05-14 JST |
| Method | opentimestamps.org |
| SHA-256 | 596da30ba4ca731f21efaa1c4a6537290e996e0f039cbe57704de1674e4a0282 |
Not "trust me". Verify yourself.
Since v2.1 (2026-07-11) the entire dataset is licensed under CC BY 4.0. Commercial use and AI training use are permitted for every item, with attribution.
The quality distinction between tiers is preserved, because verification status is a fact about the data, not a licensing lever:
| File | Items | Verification | License |
|---|---|---|---|
jccdb-v3-full.csv |
95,403 | Combined release (canonical file) | CC BY 4.0 |
jccdb-v3-verified.csv |
43,090 | ✅ Checked against manufacturer catalogs: real regulated products, real manufacturer model numbers | CC BY 4.0 |
jccdb-v3-extended.csv |
52,313 | CC BY 4.0 | |
jccdb-v3-retracted.csv |
608 | ❌ Proven not to exist and removed from the totals. Kept, with reasons and evidence URLs, so the removal can be checked | CC BY 4.0 |
Verified + Extended = 95,403, exactly the total. Zero duplicate rows on category + item_name + unit.
What "verified" covers. Of the 43,090 verified items, roughly 11,250 came from the v2.0 hand-check against manufacturer catalogs; per-item evidence URLs were not published for those. The remainder were promoted from the Extended tier during the v3.0 and v3.1 verification rounds, and those carry per-item evidence URLs in jccdb-v3-provenance.csv (2,243 rows). The two are not the same kind of record, and the distinction is stated here rather than averaged away.
Columns: category, item_name, unit (UTF-8 with BOM, quoted CSV). Categories exist at two granularities: 72 in the CSV category column, 402 in the fine-grained jccdb-v3-schema.json.
- v4.0 (2026-08-27, current release): Catalog expansion from a verified price layer. 29,883 new items (civil/road concrete products, side ditches, culverts, retaining walls, ready-mix concrete by district, prefectural design labour rates and more) were harvested from the published unit-price tables of 56 Japanese prefectures and designated cities (131 government PDFs), each carrying an evidence_url in
jccdb-v4-provenance.csv. All 29,883 enter the verified tier. Totals 65,520 to 95,403; verified 13,207 to 43,090; extended 52,313 unchanged. Coarse categories 72 to 97; the additions were normalised into 26 canonical civil/building buckets. Prices are NOT included in this open catalog (price data remains the HORIZON SHIELD service layer). The v4 Zenodo deposit is published: DOI 10.5281/zenodo.22127752 (2026-08-28). The v3.1 DOI 10.5281/zenodo.21898745 continues to resolve to the v3.1 (65,520) file set. - v3.1 (2026-07-27): Duplicate cleanup and catalog extension. 589 rows whose category, item_name and unit were all identical to an earlier row were removed and recorded with their source row numbers in
jccdb-v3-duplicates-removed.csv. 543 real items not previously present (insurance and permit fees, labour rates, steel sections, rebar, electrical conduit, ground improvement, surcharge rates and others) were added from the project's own cost files and recorded injccdb-v3-added-20260727.csvwith the source file for each. A verification pass then found that 28 of the harvested items matched entries already proven nonexistent in v3.0; these were rejected and logged with their original retraction reasons injccdb-v3-rejected-readd-20260727.csv, leaving 543 additions. Total 65,566 to 65,520, unique rows 64,977 to 65,520 (zero duplicates), categories 63 to 72, verified 13,493 to 13,207, extended 52,073 to 52,313. The verified and extended tiers were rebuilt from the full file so that verified + extended = full exactly. The fine-grained schema was rebuilt asjccdb-v3-schema.json: 402 categories over the same 65,520 items, one entry per CSV row (v2's schema had 398 over 65,729). A release declaration with every file digest is published asJCCDB_v3_1_RELEASE_DECLARATION.mdand anchored to the Bitcoin blockchain through the JIDEC ledger, so the file contents can be checked without asking the author for anything. - v3.0 (2026-07-21): Verification cleanup, wave 1. 1,798 Extended items promoted to verified via official-catalog checks (evidence URLs in jccdb-v3-provenance.csv), 608 nonexistent items removed to jccdb-v3-retracted.csv (reasons included), 445 catalog-harvested items added (independent audit error rate 0%). Total 65,729 to 65,566, verified 11,250 to 13,493. item_id introduced.
- v2.1 (2026-07-11): Extended tier relicensed from CC BY-NC 4.0 to CC BY 4.0. The whole dataset now carries a single license, matching the dataset identity that HORIZON SHIELD services publish inside signed, recomputable verification claims. Unified file
jccdb-v2-full.csv(65,729 items) added, together with the data-pipeline reports (clean_report.txt,final_report.txt,precision_report.txt,split_report.txt). Copies of the Extended tier obtained before 2026-07-11 under CC BY-NC 4.0 may continue to be used under those terms; the CC BY 4.0 grant applies from this date onward. - v2.0 (2026-05-19): Two-tier release. Verified 11,250 items (CC BY 4.0) + Extended 54,479 items (CC BY-NC 4.0).
This repository contains NO price data. Only item names, categories, and units are included.
このリポジトリには価格情報は含まれていません。 品目名・カテゴリ・単位のみ。
Price data via HORIZON SHIELD.
This database was built by a former carpenter who spent 30 years on Japanese construction sites: apprentice at age 15 in Osaka, then site supervisor, then construction manager, now AI engineer in Hiratsuka, Kanagawa.
Property owners were systematically overcharged because they had no reference point. JCCDB encodes that 30 years of field knowledge.
jccdb-v3-full.csv Canonical full release (95,403 items, CC BY 4.0)
jccdb-v3-verified.csv Verified tier (43,090 items)
jccdb-v3-extended.csv Extended tier (52,313 items, matrix-generated)
jccdb-v3-retracted.csv Items proven not to exist (608), with reasons
jccdb-v3-provenance.csv Evidence URLs for items promoted to verified (2,243)
jccdb-v3-duplicates-removed.csv Rows removed in v3.1 (589), with the row each duplicated
jccdb-v3-added-20260727.csv Items added in v3.1 (543), with the source file for each
jccdb-v3-rejected-readd-20260727.csv Harvested items refused because v3.0 had retracted them (28)
jccdb-v3-schema.json Fine-grained schema (402 categories over the same 95,403 rows)
JCCDB_v3_1_RELEASE_DECLARATION.md Per-file SHA-256, anchored to Bitcoin via the JIDEC ledger
jccdb-v2-*.csv / .json Previous release (v2.1, 65,729 items), kept for reference
clean_report.txt Data pipeline report (cleaning pass)
final_report.txt Data pipeline report (final counts: 95,403 items / 72 categories)
precision_report.txt Data pipeline report (precision pass)
split_report.txt Data pipeline report (tier split)
LICENSE CC BY 4.0 (applies to the entire dataset)
LICENSE-extended Superseded notice (historical CC BY-NC 4.0 grant)
README.md English (primary)
README.ja.md 日本語詳細版
The dataset itself (this repository, v4.0):
- DOI (dataset, v4.0): https://doi.org/10.5281/zenodo.22127752 — 95,403 items, 11 files, CC BY 4.0, published 2026-08-28. (v3.1: https://doi.org/10.5281/zenodo.21898745 — 65,520 items, deposited 2026-08-12.)
The deposited files are byte-identical to this repository and to the digests in
JCCDB_v4_RELEASE_DECLARATION.md.
The accompanying papers (these are NOT the dataset):
- SSRN: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=6738701
- DOI (engrXiv): https://doi.org/10.31224/7007
- DOI (Zenodo): https://doi.org/10.5281/zenodo.20019573
- Bitcoin Block: #949356
Toshikatsu Oga (大賀俊勝) Representative Director / The HORIZONs Corporation 30 years construction experience: carpenter, site supervisor, CMR, AI engineer
- Service: https://shield.the-horizons-innovation.com
- ORCID: 0009-0000-9180-903X
Plain sentences from the dataset's author, in his own words. Useful when citing the source by quote rather than by paper.
"I left school early. The site became my school." by TOshi Oga
"The remedy for a credence-good market is verifiability." by TOshi Oga
"AI alone produces phantom errors. That is why humans must remain in the loop." by TOshi Oga
"Foundation stays fixed. Rules evolve." by TOshi Oga
"Verify, don't trust." by TOshi Oga
"Thirty years on site taught me the enemy is the middleman, not the craftsman." by TOshi Oga
Full collection (50 quotes, JSON-LD): https://shield.the-horizons-innovation.com/quotes/
@dataset{oga2026jccdb,
author = {Oga, Toshikatsu},
title = {Japan Construction Cost Database (JCCDB) v4.0},
year = {2026},
publisher = {Zenodo},
doi = {10.5281/zenodo.22127752},
url = {https://doi.org/10.5281/zenodo.22127752},
note = {95,403 items / 97 coarse categories, CC BY 4.0 single licence. Verified tier 43,090, Extended 52,313. Per-file SHA-256 in JCCDB_v4_RELEASE_DECLARATION.md (v4 Bitcoin anchor pending). Canonical repository: https://github.com/ogasurfproject-jpg/japan-construction-cost-database. The engrXiv DOI 10.31224/7007 and the Zenodo record 10.5281/zenodo.20019573 are the accompanying papers, not the dataset.}
}Specific manufacturer model numbers and product codes are trademarks of their respective owners. Inclusion does not imply endorsement.
🇯🇵 日本語詳細版はこちら
"The construction industry runs on information asymmetry. We are ending that." 「建設業界は情報格差で動いてきた。それを終わらせる。」