Greg Pomerantz
43ddd3ec7f
JLPSX showed a bogus +29.3%/-22.9% 3-day wiggle in Dec 2020: Yahoo dated
the 6.824 year-end cap-gain distribution on the 12-11 record date but the
market went ex-div on 12-14 (close 30.10 -> 23.22), so the raw Adj Close
column pre-applied the adjustment 3 days before the price actually fell.
New 'history' correction op ({date: {col: value}}) patches individual OHLC
cells at bundle assembly (full build, incremental, and correction-changed
recompute paths); check_corrections validates dates/columns; 4 new tests.
scripts/scan_adj_misalign.py finds the artifact set-wide: 481 hits on 278
symbols, overwhelmingly December year-end distributions of value funds
(JLPSX's class of fund). scripts/fix_adj_misalign.py repairs it
arithmetic-only (rescale adj in [event, ex-div) by (1-f); cumulative
returns unchanged, cross-checked implied dist vs the price drop). Applied
to the only curated-fund hit (JLPSX) and its sister class JLPYX (implied
dist 6.824 both = official amount; ex-div 2020-12-14). The remaining ~276
symbols are reported in reports/adj_misalign/scan.md for a bulk run.
48 lines
1.4 KiB
JSON
48 lines
1.4 KiB
JSON
{
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"symbol": "jlpyx",
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"dedup": [
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[
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"2017-12-13",
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4.123
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],
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[
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"2018-12-12",
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4.117
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],
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[
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"2019-12-12",
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1.517
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],
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[
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"2020-12-11",
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6.824
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],
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[
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"2021-12-13",
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6.785
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],
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[
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"2022-12-13",
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4.841
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],
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[
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"2023-12-13",
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1.989
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],
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[
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"2024-12-12",
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1.347
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],
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[
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"2025-12-11",
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0.656
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]
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],
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"note": "Bulk correction from the double-listing scan (scripts/scan_double_listing.py): Yahoo listed this distribution in both the dividend and capitalGains event files (same date, same amount); one copy is spurious. The 'dedup' invariant keeps at most one copy, layout-agnostically. Mechanism verified against official filings for JLPSX/GDEUX/GSOUX/FAEVX/CVSIX/FZAGX; mechanism-inferred for this symbol (no per-fund official check). Revert the entry if a future official cross-check shows both rows were real. adj-close repair: Yahoo dated a distribution on 2020-12-11 (record date) but the price went ex-div on 2020-12-14 (close 30.29 -> 23.40, drop ~6.824); the raw Adj Close column spiked +29.1% on 2020-12-11 and snapped back later. Cells in [2020-12-11, 2020-12-14) rescaled by (1-f) so the adjusted path is smooth; cumulative returns are unchanged. Mechanism: scripts/fix_adj_misalign.py, scan: reports/adj_misalign/scan.md.",
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"history": {
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"2020-12-11": {
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"Adj Close": 11.400895
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}
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}
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}
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