COIN Monday-morning gaps vs ordinary overnight gaps (last ~3 years)
Monday opens for Coinbase have been noticeably larger in size than ordinary overnight moves, but they don’t carry a reliable directional signal. Over the last ~36 months the mean absolute Fri→Mon gap was 2.433% versus 1.800% for Tue–Fri gaps (Welch p = 0.0034), while the average signed Monday move (+0.248%) is small and statistically indistinguishable from zero. In short: weekend crypto repricing piles up into bigger openings, not into a predictable buy-or-sell bias.
This study compares COIN’s regular-session open to the prior regular close for each trading day, partitioning Fri→Mon gaps against Tue–Fri overnights and testing magnitudes (Welch t-test) and directionality (one-sample tests, sign fractions). The detailed statistics, charts, and robustness checks that support these conclusions follow below.
For COIN over the past ~3 years, are Monday-morning gaps (Friday close → Monday open) systematically larger in magnitude than ordinary weekday overnight gaps — COIN repricing to a weekend of nonstop crypto trading it couldn't participate in — even though the gap's direction carries no reliable edge? Thesis: Monday gaps run meaningfully wider than other overnight gaps because two-plus days of crypto moves pile up while the stock is shut, but they come out roughly symmetric, making it a volatility quirk rather than a tradeable directional signal.
How this was measured
Filtered COIN minute bars to US regular trading hours (Mon–Fri, 09:30–16:00 New York). For each trading day, took the RTH open (first 09:30 bar) and prior day’s RTH close (last 16:00 bar) to compute the overnight gap: gap = open_t / close_{t-1} − 1. Partitioned gaps into Monday (Fri→Mon) vs ordinary weekdays (Tue–Fri). Compared absolute-gap distributions with a Welch two-sample t-test; assessed directional bias via one-sample t-tests of signed gaps against zero and the fraction of positive gaps. All computations are within the last ~36 months of available data.
The key numbers
Reading the numbers
Monday absolute gaps average 0.024333891328212374 (N=142) versus 0.01800025516896964 for Tue–Fri (N=608); the Welch test p=0.0033703133430484575 says Monday gaps are significantly wider in magnitude. The mean signed Monday gap is 0.00248224395338233 with p=0.3872822113135215, so there is no reliable directional edge for Mondays.
The charts
This box plot puts the size of Friday→Monday absolute gaps next to ordinary overnight gaps and the whole Monday box is shifted upward: the Monday mean absolute gap is 0.0243 (n=142) versus 0.0180 for Tue–Fri (n=608). Look at the long upper whisker and the much larger Monday max (0.2072) compared with Tue–Fri max (0.1413) — Mondays show a longer tail of big moves. That visual plus the sample counts lines up with the statistical result that Monday gaps are meaningfully wider in magnitude.
The histogram of signed Friday→Monday gaps spans both directions: the min is −0.2072 and the max is 0.1092 with mean 0.00248224395338233 (n=142). Note the extreme negative outliers (down to −0.2072) while the bulk of bars sit near zero; despite a slight majority of positives (fraction positive 0.5422535211267606), the one-sample p for the Monday mean is 0.3872822113135215, so the average signed gap is not reliably different from zero. In short, Monday gaps are often larger in magnitude but not consistently biased up or down.
The Tue–Fri signed-gap histogram covers a similar central band with min −0.1125, max 0.1413 and mean 0.0021316751855639296 (n=608). The one-sample p for the Tue–Fri mean is 0.03628900153707452, indicating a small positive average across ordinary weekdays, but the Welch p comparing Monday vs Tue–Fri signed means is 0.9082371989224218, meaning Monday and other weekdays show no meaningful difference in direction. Combine that with the significant difference in absolute gaps (p=0.0033703133430484575) and the pattern is clear: Mondays are wider in magnitude but not directionally distinct.
Overnight gap summary: Monday vs ordinary weekdays
| group | N | mean_abs_gap | median_abs_gap | std_abs_gap | mean_signed_gap | median_signed_gap | fraction_positive |
|---|---|---|---|---|---|---|---|
| Monday (Fri→Mon) | 142 | 0.0243 | 0.0186 | 0.0239 | 0.0025 | 0.0044 | 0.5423 |
| Tue–Fri (prev→open) | 608 | 0.018 | 0.0137 | 0.0175 | 0.0021 | 0.0005 | 0.5132 |
The takeaway
Yes — Monday (Fri→Mon) opens are meaningfully bigger in size but not a reliable directional trade. The mean absolute Monday gap is 2.433% vs 1.800% for Tue–Fri, with N=142 Mondays and N=608 ordinary overnights and a Welch p=0.0034 (about a 3-in-1,000 chance this size difference is random). Signed Monday gaps average +0.248% (p=0.387, i.e., roughly a 39-in-100 chance this is noise) and 54.2% of Mondays are up, so there’s no clear directional edge from the weekend. Ordinary weekdays show a tiny signed mean (+0.213%) but the Mon vs Tue–Fri signed-mean comparison is p=0.908, which strongly supports no directional difference between groups. Bottom line: the weekend piles up crypto moves into larger openings on Mondays — a volatility/size quirk you can price or hedge around, but not a dependable long/short signal.
The fine print
- Analysis window: 2023-07-03 to 2026-06-30 (available minute RTH data).
- Open/close are regular-session bars (09:30 and 16:00 ET); pre/post-market moves are excluded.
- Equity gaps are heavy-tailed; Welch t-tests can be sensitive to outliers — nonparametric robustness checks are recommended.
- Results are unconditional and do not control for weekend crypto volatility or broader macro regime.