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BBB Spread Δ20d

What it is

BBB Spread Δ20d — registry key bbb_spread_20d_chg.

20-trading-day change of the BBB credit spread (percentage points), computed at capture time from trailing daily_signals.bbb_spread history. Pure data carrier for the analogue matcher’s drawdown-risk lane — no bands, no health-score contribution. The raw bbb_spread level stays display_only (subsumed by hy_oas); only its direction-of-change is the matcher dimension.

Data-pyramid tier

T1 — Signal. This metric sits at the signal layer of the platform’s six-tier data pyramid (T0 raw inputs → T5 actionable read). The tier reflects how far the value is from a raw measurement — not how strongly it is validated. Abstraction and validation are separate axes: a higher tier is not a claim of stronger evidence.

Horizon & validation

No validated skill horizon is on file for this metric — read it as context / a data carrier, not a validated edge. Stamps are added only when a gated research verdict lands.

Source

Source module: capture
Data source: computed

Derived metric — produced inside the platform (app/signals/capture.py or equivalent) rather than fetched as a raw upstream value. See the How it's computed section below for the formula.

How it’s computed

Change of the BBB credit spread over the last 20 trading rows: bbb_spread(t) - bbb_spread(t - 20 rows), in percentage points. Computed at capture time in app/signals/capture.py:_inject_bbb_spread_20d_chg from the trailing daily_signals.bbb_spread history (the value 20 rows back); NULL when fewer than 20 prior rows carry a bbb_spread. Series exists 2023+ only (zero 2022-bear coverage) — historical rows before that stay NULL and the matcher skips the dim for those analogues. Backfilled by scripts/backfill_bbb_spread_chg.py.

Where it surfaces

• API field: signals.bbb_spread_20d_chg on GET /api/v1/signals/latest
• Surface: daily_signals row (daily-cadence persistence)

Health-score / alignment role

Data carrier — no implication, no health-score contribution.

Persisted for downstream consumers (sparklines, base-rate matcher, calibration substrate) but does not classify into BULLISH / NEUTRAL / BEARISH and does not contribute to the 0-100 health score.

Release cadence

• Publishes: daily

See also

• /kb/api/get-signals-latest — API endpoint that serves this field.