--- title: "SPX Surged 2.85% and the Next Day Was Green Too — This Only Happens 53% of the Time" date: "2026-04-02 23:51:28" author: "Russell" permalink: "https://boringedge.com/spx-surged-2-85-and-the-next-day-was-green-too-this-only-happens-53-of-the-time/" categories: ["Uncategorized"] tags: [] featured_image: "https://boringedge.com/wp-content/uploads/2026/04/blog8_green_vs_red_fwd.png" featured_image_alt: "" description: "Blog 1 showed that a >2.85% day leads to below-average forward returns. But what if the very next day is..." --- ![""](https://boringedge.com/wp-content/uploads/2026/04/blog8_green_vs_red_fwd.png) *Blog 1 showed that a >2.85% day leads to below-average forward returns. But what if the very next day is also green? That changes everything. Here's what 80 historical instances tell us.* The Follow-Up Question In [our previous analysis](/spx-surged-2-9-percent-history-says-dont-celebrate/), we found that SPX gaining >2.85% in a single day is not a bullish signal. The average next-day return is -0.14%, and forward returns underperform at every time horizon. But on March 31, 2026, SPX surged +2.91% — and then on April 1, it went up *again*. This raised a question: **Does a green follow-through day change the statistical picture?** The answer is yes. Dramatically. The Split: 80 vs 72 Since 1950, there have been 152 instances of SPX gaining >2.85% in a single session. The next day: - **80 times (53%)** — the next day was also positive - **72 times (47%)** — the next day was negative It's almost a coin flip. But the forward returns from these two groups are *worlds apart*. Two Completely Different Outcomes Forward returns from big up day, split by whether the next day was green or red. PeriodNext Day Green (n=80)Next Day Red (n=72)Difference 1 Day**+1.29%** (WR 100%)-1.72% (WR 0%)+3.01% 2 Days**+1.31%** (WR 78%)-1.98% (WR 22%)+3.29% 5 Days**+1.63%** (WR 76%)-2.53% (WR 38%)+4.16% 10 Days**+2.30%** (WR 72%)-2.49% (WR 38%)+4.79% 1 Month**+2.23%** (WR 66%)-1.91% (WR 46%)+4.14% 3 Months**+4.12%** (WR 71%)+0.93% (WR 54%)+3.19% Look at the 5-day numbers: **+1.63% vs -2.53%**. That's a 4.16 percentage point gap based on a single binary signal — whether the next day was green or red. At 10 days, the green group averages +2.30% with a 72% win rate. The red group averages **-2.49%** with only a 38% win rate. Same starting condition (big up day), completely different trajectories. Win Rates Tell the Same Story Win rates at each time horizon, split by next-day direction. The green group maintains a 66-76% win rate across all horizons. The red group sits at 22-54% — consistently below a coin flip at short to medium timeframes. This is the key insight: **the next day's direction after a big up day is a genuine signal, not noise.** But What If You Bought After Seeing the Green Day? There's a practical problem. You can only know the next day was green *after* it closes. So if you use this as a signal, your entry is Day 1's close — not the big up day's close. If you entered at Day 1 close after confirming the green follow-through. Period (from Day 1 close)Avg ReturnWin Rate Day 2+0.02%45% Day 3+0.19%54% 5 Days+0.34%61% 10 Days+0.99%62% 1 Month+0.94%58% 3 Months+2.82%62% The returns are positive but modest. Day 2 is essentially a coin flip (45% WR). The edge builds slowly — by 3 months, you're looking at +2.82% with a 62% win rate. **Translation:** The confirmation signal is real, but most of the alpha was captured in the original big up day + follow-through. By the time you confirm the signal and enter, you're buying the tail end of the initial momentum. What This Means for March 31, 2026 SPX surged +2.91% on March 31, then gained +0.72% on April 1. This puts us in the "green next day" camp — the historically favorable group. Based on the 80 prior instances in this group: - **5-day outlook:** +1.63% avg, 76% win rate - **10-day outlook:** +2.30% avg, 72% win rate - **1-month outlook:** +2.23% avg, 66% win rate - **3-month outlook:** +4.12% avg, 71% win rate Compare this to the *overall* >2.85% day numbers from our previous article (which included both green and red next days): the all-event averages were -0.36% at 5 days and +0.26% at 1 month. The green-follow-through group outperforms at every horizon. Notable Historical Instances Some of the most famous green-follow-through events: - **2020-03-24** (Post-COVID crash): Big up +9.4%, next day +1.2% → 1-month: **+14.3%** - **2019-01-04** (Post-Christmas): Big up +3.4%, next day +0.7% → 1-month: **+8.1%** - **2018-12-26** (Christmas bottom): Big up +5.0%, next day +0.9% → 1-month: **+7.1%** - **2025-05-12**: Big up +3.3%, next day +0.7% → 1-month: **+3.0%** - **2011-11-28**: Big up +2.9%, next day +0.2% → 1-month: **+4.8%** These aren't cherry-picked — the group average is genuinely positive. However, note that some instances still led to losses at 1 month (34% of the time). This is a probability tilt, not a guarantee. Why the Next Day Matters A big up day by itself is ambiguous. It could be: - **A dead cat bounce** in a bear market — sharp relief rally that immediately reverses. - **A genuine inflection point** — the market found a floor and buyers are stepping in. The next day acts as a **confirmation filter**. When the market goes up again the day after a massive rally, it suggests the buying wasn't just short-covering or panic buying. There's follow-through conviction. When the next day is red, it suggests the big up day was exactly what our previous article warned about — a volatility spike in a chaotic market, not a signal of strength. The Boring Edge Takeaway - **A big up day alone is a warning sign** (see our [previous analysis](/spx-surged-2-9-percent-history-says-dont-celebrate/)). Forward returns are below average at every horizon. - **A big up day + green follow-through is a genuine positive signal.** The 80 historical instances show +2.23% at 1 month (66% WR) vs -1.91% (46% WR) for the red-follow-through group. - **But the signal is already in the price.** If you waited for confirmation and bought at Day 1's close, your edge is much smaller: +0.94% at 1 month with a 58% win rate. - **Current read (April 2026):** March 31's +2.91% surge + April 1's +0.72% follow-through places this event in the historically favorable cohort. The data tilts cautiously bullish over the next 1-3 months. *This analysis covers 19,182 trading days from January 1950 to April 2026. All forward returns are based on closing prices. This is not financial advice — it's what 75 years of data says happened in similar situations.* ***Methodology:** We define "big up day" as any session where SPX closes >2.85% higher than the previous close (n=152). "Green follow-through" means the very next trading day also closed positive. Forward returns are calculated from the big up day's close. This is an extension of our [original >2.85% day analysis](/spx-surged-2-9-percent-history-says-dont-celebrate/).*