True — and it is the best example of why a big number can be untradeable.
The Sunday reopen produces the most extreme readings in our entire dataset: USD/CHF closes higher 62.8% of the time against 49.8% elsewhere. Sunday is under 4% of all our buckets and supplies 6 of the 20 strongest. It is also the widest-spread hour of the week — EUR/USD quotes roughly 1.5–3 pips there against 0.1–0.8 at the London–New York overlap. Price the spread correctly and almost none of it survives. Our own dashboard now charges the Sunday reopen triple spread for exactly this reason.
| Market | In the window | Rest | z | Movement | Samples |
|---|---|---|---|---|---|
| USD/JPY | 61.9% | 50.8% | 10.4 | 215% of normal | 2,462 |
| USD/CHF | 62.8% | 49.8% | 10.3 | 238% of normal | 1,738 |
| USD/CAD | 57.7% | 49.5% | 8.7 | 173% of normal | 3,179 |
| GBP/JPY | 60.2% | 51.1% | 8.1 | 190% of normal | 2,252 |
| EUR/JPY | 58.6% | 51.1% | 7.6 | 190% of normal | 2,791 |
| EUR/GBP | 58.3% | 49.0% | 6.5 | 142% of normal | 1,344 |
Every claim here reduces to a window on the clock or the calendar, so it can simply be checked. We compare the claimed window against the rest of the week on 23 years of hourly data across 19 markets, measuring two separate things the folklore tends to conflate: direction (does the window close higher more often?) via a two-proportion z-test, and movement (is the average move bigger or smaller?). A window can be perfectly ordinary in direction and genuinely quieter in movement — saying which is the entire point.
The bar here is |z| ≥ 2, deliberately more lenient than the |z| ≥ 3 this site applies to its own numbers: when testing someone else's claim, failing to reject it even at a lenient bar is the stronger statement.