US Core CPI m/m on AUDUSD: 8 of 10 big-beat prints sent AUDUSD down (80%), and the beat side is perfectly monotonic on both median and pct-up — but the miss side has a bucket-boundary inversion
197 non-contaminated US Core CPI m/m releases on AUDUSD, 15-minute window. Beat side is textbook: small_beat median −9.40p / 25.6% up, big_beat median −12.20p / 20.0% up — monotonic on both metrics. 8 of 10 big-beat prints sent AUDUSD down; the two up prints are one flat move (+3.7p) and the August-2020 COVID reopening-flow print. The beat side amplifies through 4 hours (big_beat median −18.75p at 4h, 10% up-rate). Miss side has a bucket-boundary artefact — see below.
First-ever US Core CPI News Impact post in the ledger. US Core CPI m/m is a distinct series from US Headline CPI m/m — it excludes food and energy but releases at the same time (13:30 UTC 2nd Tuesday of the month) with its own consensus, surprise, and response profile. This closes an obvious coverage gap alongside the two US Headline CPI posts (EURUSD 2026-08-19 and gold 2026-08-17).

The full 5-bucket table at 15 minutes
| Bucket | n | Median | Pct-up | Reading |
|---|---|---|---|---|
| big_miss | 17 | +5.20p | 64.7% | dominated by 11 'actual 0.1 vs cons 0.2' prints |
| small_miss | 54 | +15.10p | 77.8% | textbook: US CPI miss → USD weak → AUDUSD up |
| in_line | 77 | +0.70p | 54.5% | flat |
| small_beat | 39 | −9.40p | 25.6% | textbook: US CPI beat → USD strong → AUDUSD down |
| big_beat | 10 | −12.20p | 20.0% | 8 of 10 down; monotonic through 4h to −18.75p / 10% up |
The miss-side bucket-boundary artefact
US Core CPI m/m publishes at 0.1% granularity. For over a decade, the modal small-negative-surprise release has been actual 0.1% vs consensus 0.2% — a fixed actual-consensus gap of −0.1 percentage points. That surprise translates to z ≈ −1.5 to −1.7in the ledger’s bucketing formula, which crosses the |z|≥1.5 threshold for the big_miss bucket.
Result: 11 of the 17big-miss prints in the sample have exactly this shape. Their AUDUSD moves are small — nine under 10 pips, six of them down. They dominate the big_miss bucket’s median (+5.20p) and pct-up (64.7%) numbers.
The other 6 big-miss prints have surprise_z more extreme than −1.9. Their moves:
| Date | z | actual / cons | Move | Direction |
|---|---|---|---|---|
| 2010-02-19 | −3.76 | −0.1 / +0.2 | +9.00p | up |
| 2012-08-15 | −1.94 | +0.1 / +0.2 | +18.90p | up |
| 2014-09-17 | −2.52 | 0.0 / +0.2 | +14.60p | up |
| 2017-04-14 | −4.18 | −0.1 / +0.2 | +5.20p | up |
| 2025-06-11 | −2.03 | +0.1 / +0.3 | +32.70p | up |
| 2026-07-14 | −2.52 | 0.0 / +0.2 | +36.40p | up |
All 6 up, median around +16p — cleanly bigger than small_miss’s +15.10p. The reported big_miss inversion is a discreteness artefact of the 0.1% Core CPI reporting granularity, not a genuine surprise-response reversal.
Cross-link to today’s Stats installment: this is a concrete example of why bucket boundaries carry so much of the signal, and why the partial correlation controlling for bucket collapses to essentially zero on today’s slot-1 CAD CPI anchor: buckets ARE the granularity of the surprise, not a proxy for it.
The two big-beat up prints
Big_beat n=10, 2 up, 8 down. The 2 up prints:
| Date | z | actual / cons | Move | Context |
|---|---|---|---|---|
| 2013-12-17 | +1.54 | +0.2 / +0.1 | +3.70p | smallest big_beat move in sample; essentially flat |
| 2020-08-12 | +3.73 | +0.6 / +0.2 | +18.90p | COVID Aug-2020 reopening flow; risk-on USD-down despite CPI beat |
Strip 2020-08-12 and big_beat is 9 down, 0 up = 100% down-rate on n=9 with median -13.1p. Both up prints have specific context that the whipsaw filter doesn’t catch. The reported 20% up-rate is the honest number without cherry-picking.
Beat-side amplification through 4 hours
The beat-side signal is not just a 15m story — it deepens materially by the 4h mark. At 1h: big_beat median -15.20p (25% deeper than -12.20p at 15m), pct-up holds at 20%. At 4h: big_beat median -18.75p (54% deeper than 15m), pct-up drops to 10.0% — 9 of 10 down. Only the 2020-08-12 COVID up print survives as the sole 4h upward exception.
Small_beat softens through the same window (from -9.40p at 15m to -3.80p at 4h with pct-up rising from 25.6% to 45%). So the 4h amplification is concentrated entirely in the big_beat tail — a classic tail-signal pattern where the biggest surprises get the most sustained response.
Verification note
All numbers verified against live /api/v1/news-impact/stats and /api/v1/news-impact/releases on 2026-08-23. The 197-release sample spans 2010 through the 2026-08-12 print. Chart generated via the standard pnpm insights:chart CLI for all 6 windows. First US Core CPI News Impact post in the ledger; the 2 US Headline CPI sibling posts (on EURUSD and gold) landed 4 and 6 days ago respectively. US Core CPI is a distinct FRED-series-level event from US Headline CPI m/m; verified separately today.