The takeaway
ProShares Short 20+ Year Treasury shows a moderate seasonal pattern over 10 years of data — strongest in September (+2.2%) and softest in November (−1.3%).
Right now
In July, the fund has fallen 40% of years, averaging −0.9%, roughly 3.1 pts behind the S&P 500.
The full picture
ProShares Short 20+ Year Treasury's most dependable month has been September, higher in 9 of 10 years; November has been its least reliable, up just 20% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Win rate % | ||||||||||||
| Median return % | ||||||||||||
| 2025 | ||||||||||||
| 2024 | ||||||||||||
| 2023 | ||||||||||||
| 2022 | ||||||||||||
| 2021 | ||||||||||||
| 2020 | ||||||||||||
| 2019 | ||||||||||||
| 2018 | ||||||||||||
| 2017 | ||||||||||||
| 2016 |
Month by month
The fund's clearest edge over the S&P 500 lands in September (+2.4 pts); it has trailed the market most in November (−3.7 pts).
“vs S&P” is ProShares Short 20+ Year Treasury’s average for a month minus the S&P 500’s average for that same month — isolating ProShares Short 20+ Year Treasury’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, September has closed higher 80% of the time versus 90% across the last 10 years — the pattern is holding.
Figures are the typical (median) September return and how often it rose — the last 5 years versus the last 10(the heatmap’s default window). This verdict stays anchored to that 10-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
The seasonal story is really one month's story — September. It has closed higher in 9 of 10 Septembers, a concentration the rest of the calendar can't touch.
The strength looks broad-based rather than freakish: its average (+2.2%) and median (+2.0%) sit close together, so no single blow-out year is flattering the figure. Better still, that strength is the fund's own and not just a buoyant market — September has outpaced the S&P 500 by +2.4 points on average. It is the more striking for the company it keeps — September is a losing month for most of the market, where barely 39% of names gain ground.
It doesn't stand entirely alone — January, February, and April have leaned firm as well, if less emphatically. At the other end of the calendar, November has been the soft spot — the weakest of 6 months that average a loss (−1.3%), and the edge isn't year-round — the fund has trailed the S&P 500 in November, July, and March.
One run worth flagging just ended: a 9-year streak of positive Septembers was snapped by a −3.8% close in 2025. Reassuringly, the tendency has held its shape: the recent five years still track the years behind them.
For a fund this dependable in September, the sharper question is the rest of the year — outside its strong stretch, the calendar gives far less to lean on.
Short answers on the fund's best month (September), its worst (November), and whether it really trades seasonally.
Yes, to a moderate degree. Since 2016 its best month (September, +2.2%) has run well ahead of its worst (November, −1.3%) — the heatmap above shows how steady that gap has been year to year.
September has been the strongest, averaging +2.2% and closing higher in 9 of 10 years since 2016.
It's the weakest, averaging −1.3% — historically a soft spot, though it still varies from year to year.
Explore
These names have the strongest July track records on record — a starting point for comparison.
Before you trade