spb/firc0001_uqo

1# Universe definition (frozen for UQO WP 28, build of 2026-10-27/28)23**Estimand.** Current constituents at a snapshot date, approximated by fund holdings. Not historical point-in-time Russell 3000 membership (no licensed constituent history was available).45| Item | Value |6|---|---|7| Primary source | iShares Russell 3000 ETF (IWV) `latest-holdings.csv`, "Fund Holdings as of Oct 23, 2026", fetched 2026-10-27 (`data/metadata/russell3000_constituents.json`: `source`, `holdings_as_of`, `fetched_at`) |8| Secondary source | S&P 500 constituent table (Wikipedia), cached 2026-05-25 (`sp500_constituents.json`, 503 rows / 500 CIKs) |9| Identifier mapping | ticker → CIK via SEC `company_tickers.json` (fetched 2026-10-27); tickers normalised (`BRK B` → `BRK-B`) |10| Exclusions | asset class ≠ Equity; CVR / escrow / rights lines; tickers with no SEC CIK (FDIC-filing banks). The 21 unmatched lines are listed in the `unmatched` field of the artifact. |11| Result | 2,587 equity lines → 2,555 CIKs (share classes collapsed) → merged with S&P 500 → **2,564 issuers** (491 in both, 9 S&P-only, 2,064 Russell-only) |12| Filing scope | Forms 10-K, 10-Q, 8-K (primary document only, no amendments, no exhibits), filed 2010-01-01 → 2026-10-27 |13| Observed | 2,499 issuers with ≥1 filing; 65 without (foreign private issuers filing 20-F/40-F; FDIC banks) — `data/issuers_without_filings.csv` |14| Frozen artifact | `data/metadata/universe.json` (`built_at` 2026-10-27), copied to the paper folder under `data/` |1516**Open items (not implemented):** SHA-256 of the source files; per-row match confidence; membership dates; security-vs-issuer table (`universe_snapshots`); resolution of ticker changes and spin-offs over the sample period; a licensed historical constituent list.17