SEP · ISSUE 36 · September 3, 2026
CALENDAROn September 30, Wall Street sells without thinking
September is historically the worst month. The second half is the weakest. And at month-end there's a mechanical sell almost nobody explains to you.
SEPTEMBER (HISTORY)
worst month
second half the weakest
PENSIONS FUNDED
112%
sell equities on Sep 30
AFTER SEP 30
rally
in midterm years
THE DATE
SEP 30
↓ mechanical quarter-end equity selling
Many pension plans are 112% funded: they made more than they need. To lock in the win, at quarter-end they sell stocks and buy bonds. It isn't a market opinion, it's an accounting rule that runs on its own.
DATA
THE NUMBER112%
112%
▲ funding level of many pension plans
It's like closing out a winning bet early: not out of fear, but because the fund's own rules force it to protect the gain.
When a pension plan is 112% funded, it has more than enough to pay what it promised. And when there's a surplus, the rulebook says protect it: sell stocks, buy bonds.
- FUNDING
- — How much a plan holds versus what it must pay out in the future.
- REBALANCE
- — Resetting a fund back to its target mix of assets.
KEY
THE IDEAThe calendar is ugly, then it turns
“The second half of September weighs by calendar, not by fear. What matters isn't the dip: it's that the best stretch of the year tends to start right after.”
Seasonality isn't magic: it's the sum of fund rules that repeat on the same dates every year.
- SEASONALITY
- — Market patterns that repeat at the same times each year.
- SYSTEMATIC
- — A move driven by an automatic rule, not a human decision.
SEASONALITY
THE TURNHow the calendar tends to behave in midterm years
Illustrative chart. The second-half-September dip tends to give way to the best quarter of the year in midterm cycles.
Illustrative average return by stretch. The shape, not the exact figure, tells the story: a dip, then a bounce.
- 2ND HALF
- — From the 15th to the end of the month.
- HISTORICAL AVERAGE
- — The mean of many years; no single year looks the same.
BEFORE AND AFTER
TWO PHASESThe two faces of the final quarter
UNTIL SEP 30
The weak part
- September, the worst month in the record, led by its second half.
- Quarter-end pension selling: stocks out, bonds in.
- Systematic funds amplify any drop (downside asymmetry).
FROM SEP 30
The best stretch
- In midterm years, a rally into year-end has historically begun.
- The momentum factor tends to turn up (~+6% in the second half).
- The very selling that weighs before stops weighing once the reset ends.
The same quarter has a weak part and a strong part. Confusing them makes you sell right before the turn.
- MOMENTUM
- — The strength of a trend; when it turns, it drags the rest along.
- ASYMMETRY
- — When drops weigh more than rises because of how funds trade.
WHO SELLS
WHERE IT COMES FROMWho drives the quarter-end selling (illustrative)
Sell stocks, buy bonds
Cut risk as volatility rises
Periodic weight adjustment
The only part a person decides
Illustrative split. The fact that it's mechanical is the key: it runs whatever the news does.
Rough split of month-end selling pressure. The point: almost none of it is discretionary, almost all of it is rules.
- DISCRETIONARY
- — Decided by a person, not by an automatic rule.
- VOL-CONTROL
- — Funds that cut exposure when volatility rises.
CALENDAR
COMING WEEKSThe five dates that mark the quarter's turn
| THU SEP 3 · 10:00 ET | ISM SERVICES | Medium | Pulse of the services sector; cons ~54.5. A read-through before the jobs number. |
| FRI SEP 4 · 08:30 ET | AUGUST JOBS (NFP) | High | The number of the month; options price a ~1.1% S&P move. |
| WED SEP 16 · 14:00 ET | FED MEETING | High | The biggest expected move of the month; ~64% odds of a hike priced in. |
| FRI SEP 18 · 16:00 ET | DERIVATIVES EXPIRY | Medium | Many options expire; it tends to bring extra volatility. |
| WED SEP 30 · close | PENSION MECHANICAL SELL | High | Quarter-end: pension reset. The seasonal turning point. |
If you know when fund rules fire, you understand why the market moves on specific dates.
- NFP
- — Non-farm payrolls: the monthly US jobs report.
- FOMC
- — The Fed committee that sets interest rates.
- EXPIRY
- — The day options and futures expire; it moves volume and price.
CLOSE
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- QUARTER
- — A three-month period; quarter-end resets many funds to target weights.
- RALLY
- — A sustained stretch of rising prices in the market.