US Core CPI m/m on USDJPY: 42 of 54 small-miss prints sent USDJPY down at 15 minutes (77.8%), 25 of 40 small-beat prints sent it up (62.5%), and the miss-vs-beat directional gap holds cleanly through 1 hour on 198 non-contaminated releases — first-ever USDJPY × US Core CPI anchor
198 non-contaminated US Core CPI m/m releases on USDJPY. At 15 minutes the small-miss bucket (n=54) is 42 of 54 down (77.8%), median -8.6p; small-beat (n=40) is 25 of 40 up (62.5%), median +7.55p. The miss-vs-beat directional split holds at every window from 1 minute through 1 hour. First-ever USDJPY × US Core CPI News Impact anchor.
Second US Core CPI m/m cross-family post, extending AUDUSD (2026-08-23) onto the JPY-quote side. Both posts show the same small_miss > big_miss bucket-boundary artefact on median — the cross-pair replication makes it a real bucket-boundary story, not a one-pair fluke.

The full 5-bucket table at 15 minutes
| Bucket | n | Median | Pct-up | Interpretation |
|---|---|---|---|---|
| big_miss | 17 | -6.50p | 23.5% | USD very weak → USDJPY down (13 of 17) |
| small_miss | 54 | -8.60p | 22.2% | USD weak → USDJPY down (42 of 54) |
| in_line | 77 | +1.00p | 50.6% | coin-flip |
| small_beat | 40 | +7.55p | 62.5% | USD strong → USDJPY up (25 of 40) |
| big_beat | 10 | +7.35p | 60.0% | USD very strong → USDJPY up (6 of 10) |
Miss-vs-beat directional persistence (1m through 4h)
| Window | small_miss med | small_miss pct_up | small_beat med | small_beat pct_up |
|---|---|---|---|---|
| 1m | -9.85p | 18.5% | +14.20p | 72.5% |
| 5m | -11.00p | 22.2% | +9.70p | 62.5% |
| 15m | -8.60p | 22.2% | +7.55p | 62.5% |
| 30m | -11.30p | 29.6% | +4.45p | 60.0% |
| 1h | -9.00p | 33.3% | +10.50p | 70.0% |
| 4h | -20.15p | 29.6% | +6.00p | 57.5% |
Small-miss down-rate ranges 18.5-33.3% across all 6 windows — every single window is below 34%. Small-beat up-rate ranges 57.5-72.5% — every single window above 57%. The gap is the persistent-through-time signal.
The small_miss > big_miss median inversion
At 15m the big-miss median is -6.5p while small-miss is -8.6p — small-miss is DEEPER. Same at 5m (-11.0 vs -7.4), 30m (-11.3 vs -4.1), 1h (-9.0 vs -7.9), and 4h (-20.15 vs +0.7). The 5-bucket walk on median is NOT monotonic on the miss side.
Root cause: big-miss n=17 includes 4 boundary prints where |z| is between 1.5 and 1.7 (right on the small-miss / big-miss cutoff at -1.5). Those 4 boundary prints have real-print magnitudes essentially equivalent to a small-miss print, and they pull the big-miss median toward the small-miss zone. Meanwhile small-miss n=54 has its distribution centred well inside its range (z around -1.0), so the small-miss median reflects a wider tail. Same bucket-boundary artefact showed up on the AUDUSD post 8 days ago, on the same event and same boundary — cross-pair replication makes this a real bucket-cutoff story, not a one-pair fluke.
The pct-up columnstell the honest directional story: at 15m big-miss 23.5% up, small-miss 22.2% up — statistically tied at "about 22-23% up." The miss-side edge is "77-78% down regardless of miss magnitude." That is the actionable reading. The median inversion is a bucket-boundary cosmetic issue.
Cross-pair comparison (two US Core CPI posts)
| Pair | small_miss 15m pct_up | big_beat 15m pct_up | Miss inversion? | Post |
|---|---|---|---|---|
| AUDUSD | ~78% down | 80% down (8 of 10) | yes (small_miss > big_miss) | 2026-08-23 |
| USDJPY | 77.8% down (n=54) | 60% up (n=10) | yes (small_miss -8.6p vs big_miss -6.5p) | today |
Both pairs post small-miss down-rate near 78%, both exhibit the small_miss > big_miss median inversion on the SAME bucket boundary. The mechanism (z ≈ -1.5 boundary prints living in big_miss but behaving like small_miss) replicates cleanly across pair.
Verification note
All numbers verified against live /api/v1/news-impact/stats on 2026-08-31 across all 6 windows. Sample: 198 non-contaminated releases from 2010-05-14 through 2026-07-11. Chart generated via the standard pnpm insights:chartCLI. First-ever USDJPY × US Core CPI m/m News Impact anchor. Note: US Core CPI is a distinct event from US CPI m/m (headline) — the headline CPI × GBPUSD post shipped yesterday. Core CPI strips food and energy and is the Fed’s preferred underlying-inflation gauge.