Some dump files carry a trailing 'ctime' column: an older pipeline
appended a FULL re-download of the symbol per download (up to ~28
vintages per date, 2019-2022). The consumer keeps the last row per date,
so it silently used stale (~2021) vintages where Yahoo later revised
values. scripts/clean_multivintage.py keeps, per date, the rows from the
newest ctime (event files keep distinct same-day amounts; history/split
keep the single newest row), drops the ctime column, sorts by date.
Applied to the data root and overrides/frozen (which carried the same
artifact): 1,065 files, 2,202,712 stale rows dropped.
Also: stripped 3 UTF-8 BOMs (teg/lo/krft), refreshed the event backup
with the cleaned files, and re-ran the double-listing scan: category C
(83 symbols, 18,636 repeated within-file rows) is fully explained by the
multi-vintage artifact and is now gone; A (6,589 pairs, corrected) and
B (12,366 pairs, open review list) are unchanged. Whole-set structural
QC after cleaning: 0 duplicate dates, 3 syms/15 rows of OHLC invariant
violations, 15 syms/2,897 rows of non-positive prices (mostly
long-delisted tickers), 8 unsorted files (reader sorts).
Yahoo's 2026 event-feed change (capitalGain events dropped for some
funds; no events at all for terminated tickers) can wipe good event
history on re-download. Defense in depth:
- overrides/event-backup/: last-known-good copy of every dividend/
capitalGain file (8,192 files, 58 MB); refresh with
scripts/backup_events.py after each dump update
- data.py event_file(): frozen > data-root (while populated) > backup;
used by panel reads, verify_official, and the double-listing scanner
- README: capital-gain files are mutual-fund-only in this dump; Yahoo
has no LT/ST split (tax.py taxes capg at lt_rate; the per-fund split
would come from fund-company annual tax statements or commercial feeds)
- tests: exact Timestamp .loc keys (pandas 3.x string matching returns a
Series on large DatetimeIndex)
