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The Week 3 Dead Zone: Why Markets Stall Mid-Month

Ten years of SPY data reveal a persistent calendar pattern. The 15th through 21st of each month has cost investors nearly 17 percentage points since 2015.

January 2026 8 min read

The trading calendar isn't neutral. Between 2015 and 2025, SPY returned +52% in the first week of each month, +44% in the second week, and +58% in the final week. But the third week—the 15th through 21st—lost -17%. That's 2,764 trading days with one week consistently dragging down returns.

This isn't market mythology or a cherry-picked sample. I analyzed every trading day from January 2015 through December 2025—11 years of data across different Fed regimes, bull markets, bear markets, and a global pandemic. The pattern held.

The numbers are stark. Week 3 delivered an average daily return of -0.027% compared to +0.084% for Week 1 and +0.067% for Week 2. That 10 basis point daily gap compounds significantly over time.

-16.87%
Cumulative Week 3 return (15th-21st), SPY 2015-2025
...

The weekly breakdown

I grouped all trading days by their position within each month. The results show a clear pattern: early month and late month strength, mid-month weakness.

Week Trading Days Avg Daily Return Cumulative Return Win Rate
Week 1 (1st-7th) 622 +0.084% +52.0% 56.3%
Week 2 (8th-14th) 657 +0.067% +44.0% 57.1%
Week 3 (15th-21st) 631 -0.027% -16.9% 51.7%
Week 4 (22nd-31st) 854 +0.068% +58.5% 53.5%

Week 3 is the only period with negative average returns and below-52% win rate. The 51.7% win rate means you're essentially flipping a coin during this period.

Cumulative SPY returns by week of month, 2015-2025. N=2,764 trading days.

Best and worst trading days

Drilling into specific days reveals where the gains and losses concentrate. The 2nd and 15th of each month stand out as the strongest, while the 18th and 20th are the weakest:

Strongest days of the month

Day Observations Avg Return Cumulative Win Rate
2nd 88 +0.213% +18.8% 64.8%
15th 90 +0.212% +19.1% 58.9%
4th 84 +0.163% +13.7% 53.6%
26th 89 +0.160% +14.3% 52.8%
8th 95 +0.139% +13.2% 61.1%

Weakest days of the month

Day Observations Avg Return Cumulative Win Rate
18th 90 -0.160% -14.4% 56.7%
20th 90 -0.136% -12.3% 48.9%
11th 94 -0.127% -11.9% 55.3%
31st 54 -0.112% -6.0% 40.7%
3rd 89 -0.088% -7.8% 53.9%

The 2nd of each month has the highest win rate at 64.8%—nearly two-thirds of the time, markets close higher. The 31st has the lowest win rate at just 40.7%. This month-end weakness is notable given the common perception of month-end window dressing driving prices up.

Sector patterns

The calendar effect varies by sector. Some sectors amplify the Week 3 weakness; others are immune. Here's how the major sector ETFs performed:

Sector Week 1 Week 2 Week 3 Week 4
XLK Technology +4.4% +88.0% -2.6% +85.3%
XLF Financials +60.8% +23.9% -15.7% +57.8%
XLV Healthcare +41.0% +26.2% +14.5% +15.2%
XLP Staples +38.7% +17.4% -12.9% +15.9%
XLU Utilities -37.2% +27.6% -15.3% +53.7%

Healthcare (XLV) is the only sector positive in Week 3. While SPY lost 17% cumulatively in Week 3, Healthcare gained 14.5%. This defensive sector provides a natural hedge for the mid-month dead zone.

Technology (XLK) shows the most extreme pattern: Week 2 gains dwarf all other periods at +88%, but Week 1 is nearly flat at +4.4%. Financials (XLF) show the opposite—Week 1 is strongest at +60.8%.

Calendar rotation strategy

Overweight Financials in Week 1, Tech in Week 2, Healthcare in Week 3, and return to cyclicals in Week 4. This sector rotation exploits the calendar patterns rather than fighting them.

First Friday effect

The first Friday of each month—typically when the Jobs Report (NFP) is released—shows distinct behavior:

Day Type Days Avg Return Win Rate
First Friday (Jobs Day) 123 +0.100% 59.3%
All Other Days 2,641 +0.047% 54.3%

First Fridays deliver double the average daily return and 5 percentage points better win rate than other days. Markets tend to rally on Jobs Day regardless of whether the number beats or misses expectations—the resolution of uncertainty itself appears bullish.

Stocks for defensive positioning

Given Healthcare's unique strength in Week 3, here are quality Healthcare names to consider for mid-month positioning:

Healthcare (Week 3 Defense)

Ticker Company Mkt Cap P/E ROE Margin 3M Ret
LLY Eli Lilly $851B 75.2 67.9% 24.7% +23.5%
UNH UnitedHealth $497B 21.9 22.6% 5.7% -11.3%
JNJ Johnson & Johnson $353B 14.9 22.9% 15.9% +7.4%
ABBV AbbVie $324B 42.6 65.9% 13.3% +10.5%
MRK Merck $247B 14.3 46.2% 20.9% -2.4%

Consumer Staples (Additional Defense)

Ticker Company Mkt Cap P/E ROE Div Yld 3M Ret
PG Procter & Gamble $338B 21.0 32.1% 2.89% -2.2%
KO Coca-Cola $303B 23.3 47.0% 2.90% +4.8%
PEP PepsiCo $200B 27.7 38.9% 3.84% -3.9%
CL Colgate-Palmolive $68B 23.5 545% 2.44% +8.0%
TGT Target $51B 13.4 24.9% 4.06% +20.4%

Technology (Week 2 Play)

Ticker Company Mkt Cap P/E ROE Margin 3M Ret
NVDA NVIDIA $4.5T 45.6 103.8% 53.0% -2.8%
GOOG Alphabet $4.0T 32.1 35.0% 32.2% +26.9%
AAPL Apple $3.8T 34.1 164.1% 26.9% -2.2%
MSFT Microsoft $3.4T 32.6 31.5% 35.7% -11.5%
CSCO Cisco Systems $297B 28.8 22.3% 17.9% +4.6%

Financials (Week 1 Play)

Ticker Company Mkt Cap P/E ROE Div Yld 3M Ret
JPM JPMorgan Chase $851B 15.3 16.0% 1.86% +1.7%
BAC Bank of America $387B 12.7 10.2% 2.04% +1.6%
MS Morgan Stanley $301B 18.4 15.1% 2.04% +15.4%
GS Goldman Sachs $291B 17.5 13.8% 1.46% +25.7%
WFC Wells Fargo $277B 13.4 11.8% 1.92% +4.6%

Summary