Share of sessions that closed higher, by weekday, ES and NQ
- Monday
- The other four weekdays
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October 31, 2026 · 4 min read
The Monday Effect in ES and NQ, Checked Against the Other Four Days
ES closed higher on 56.5% of Mondays since 2011 and on 54.0% of the other weekdays, and its average Monday change matched the other days to three decimals. Of the weekday effects tested five looks at a time, the ones that hold are about range, not direction: Monday sessions ran 7.1% narrower than their 20-session average.
The Monday effect is one of the oldest calendar patterns in market research: stock returns were found to be weaker on Mondays than on other days, often blamed on bad news held over the weekend. It still gets quoted, sometimes as a Monday weakness and sometimes, lately, as a Monday strength. Checking it means testing all five weekdays, and five weekdays are five looks. The question is whether any weekday differs from the other four by more than the best of five chance results would.
Direction: how often each weekday closed higher
We took every regular session on S&P 500 futures (ES) and Nasdaq-100 futures (NQ), measured the change from the previous close, and grouped the sessions by weekday. Each weekday is compared with the other four together.
| Market | Weekday | Sessions | Closed higher | 95% interval | Average change | 95% interval |
|---|---|---|---|---|---|---|
| ES | Monday | 797 | 56.5% | 53–60% | +0.050% | −0.03% to +0.13% |
| ES | Tuesday | 805 | 52.0% | 49–55% | +0.076% | +0.01% to +0.15% |
| ES | Wednesday | 817 | 55.3% | 52–59% | +0.057% | −0.02% to +0.13% |
| ES | Thursday | 814 | 53.7% | 50–57% | +0.022% | −0.05% to +0.10% |
| ES | Friday | 738 | 55.0% | 51–59% | +0.043% | −0.03% to +0.12% |
| ES | Every session | 3,971 | 54.5% | +0.050% | ||
| NQ | Monday | 706 | 60.1% | 56–64% | +0.109% | +0.01% to +0.20% |
| NQ | Tuesday | 711 | 55.0% | 51–59% | +0.085% | −0.00% to +0.17% |
| NQ | Wednesday | 713 | 57.2% | 54–61% | +0.123% | +0.03% to +0.22% |
| NQ | Thursday | 713 | 53.2% | 50–57% | +0.006% | −0.09% to +0.10% |
| NQ | Friday | 646 | 55.1% | 51–59% | +0.029% | −0.07% to +0.13% |
| NQ | Every session | 3,489 | 56.1% | +0.071% |
On ES, Mondays closed higher 56.5% of the time against 54.0% for the other four weekdays, a gap of 2.5 points with a bootstrap p of 0.22. The average Monday change, +0.050%, is the same as the average of the other days to three decimals (p = 0.99). On NQ the Monday gap is wider: 60.1% against 55.1%, 4.9 points, at p = 0.013. That is the strongest direction result of the twenty, and it falls just short of the 0.01 that the best of five looks needs. The NQ Monday average, +0.109% against +0.061%, is at p = 0.41.
No weekday's average change, and no weekday's share of up closes, differs from the other four at p ≤ 0.01 in either market. The weakest day on average was NQ Thursday, +0.006% against +0.088% for the rest, at p = 0.16.
Average close-to-close change by weekday, with 95% intervals
- Clears the five-look bar (p ≤ 0.01)
- Does not
- Every session (line)
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Range: where the weekday shows
The size of the session is another matter. Comparing each session's range with the average range of the 20 sessions before it, Mondays are consistently quieter and the middle of the week is busier.
| Weekday | ES sessions | ES range against its 20-session average | ES p | NQ sessions | NQ range against its 20-session average | NQ p |
|---|---|---|---|---|---|---|
| Monday | 795 | −7.1% | < 0.001 | 703 | −4.9% | < 0.001 |
| Tuesday | 816 | +1.4% | 0.24 | 714 | +1.4% | 0.37 |
| Wednesday | 813 | +8.1% | < 0.001 | 709 | +7.0% | 0.003 |
| Thursday | 812 | +9.2% | < 0.001 | 710 | +6.7% | 0.014 |
| Friday | 799 | +3.1% | 0.99 | 697 | +3.6% | 0.64 |
On ES a Monday session ran 7.1% below its 20-session average, while the other four weekdays ran 5.5% above theirs, a gap of 12.6 points. On NQ the Monday gap is 9.6 points. Five of the ten range comparisons clear p ≤ 0.01: Monday, Wednesday and Thursday on ES, Monday and Wednesday on NQ. A likely part of the reason: news that arrives over the weekend is mostly absorbed overnight, before the regular session opens, and the scheduled releases that widen ranges, the Fed's statements among them, cluster in the middle of the week.
Two eras
Split in two, the Monday direction result changes sign. In 2011–2018 the ES Monday averaged −0.010% against +0.061% for other days, and closed higher 51.8% of the time against 54.5%: a faint version of the classic Monday weakness. In 2019–2026 it averaged +0.109% against +0.039% and closed higher 61.0% of the time against 53.5%. NQ moved the same way, from +0.024% against +0.075% to +0.172% against +0.051%. The narrower Monday range held in all four market-eras.
| Market | Era | Mondays | Monday closed higher | Other days closed higher | Monday average | Other days average | Monday range against average | Other days range |
|---|---|---|---|---|---|---|---|---|
| ES | 2011–2018 | 394 | 51.8% | 54.5% | −0.010% | +0.061% | −5.1% | +5.3% |
| ES | 2019–2026 | 403 | 61.0% | 53.5% | +0.109% | +0.039% | −9.1% | +5.6% |
| NQ | 2013–2018 | 303 | 57.4% | 55.3% | +0.024% | +0.075% | −2.2% | +5.1% |
| NQ | 2019–2026 | 403 | 62.0% | 55.0% | +0.172% | +0.051% | −7.0% | +4.3% |
What the number does and does not mean
In these futures since 2011, the weekday has said little about direction. No weekday's average change or share of up closes clears the bar that five looks set, and the Monday result that came closest, NQ's 60.1%, comes from an era split whose two halves point opposite ways. A weekday pattern that reverses between halves of the sample is a description of those years, not a property of Mondays. The weekday does say something about size: Monday regular sessions have been narrower than the days around them in both markets and both eras, and mid-week sessions wider. That is a statement about how much the market moves, not which way.
Reading the next Monday effect stat
- Looks: a stat about one weekday was chosen from five. Ask how the other four did, and judge the best of five as the best of five.
- Era: the Monday direction flipped between 2011–2018 and 2019–2026 here. Ask for both halves of the sample.
- Measure: a quieter Monday is a range result. It says nothing about whether Monday closes higher.
Data and method. E-mini S&P 500 (ES) and E-mini Nasdaq-100 (NQ) futures, regular sessions (9:30 am to 4:00 pm ET, 1:00 pm on early-close days), ES from 3 January 2011 and NQ from 2 January 2013, both to 22 October 2026, the last session on file. The change is close to close: the previous trading day's regular-session close to this one's, so Monday's change includes the weekend. Both closes must sit in one contract and on consecutive trading days, so a change across a contract roll, a holiday or a missing session is left out. The range is the session's high minus low as a share of its open, divided by the average of the same ratio over the 20 sessions before it, which is known at the open. Each weekday is compared with the other four. Intervals for the share of sessions that closed higher are 95% Wilson intervals; intervals for an average are the mean plus or minus 1.96 standard errors. The p values for each weekday-against-the-rest difference come from a moving-block bootstrap with blocks of 20 sessions and 4,000 resamples, which keeps volatility clustering. Five weekdays make five looks per market per measure, so a difference counts at p ≤ 0.01 (0.05 divided by 5). Three measures on two markets make 30 looks in all.