Momentum · month-end rule · Healthcare
12-1 Momentum on Intuitive Surgical
What the play says
Latest reading: 12-1 return −15.7%
ISRG with the play, last two years
Shading shows the play's call from the close that triggered it.
Return from 12 months to 1 month ago
Dashed line at 0.
Growth of $10,000 since 2005
Log scale. After trading costs, with T-bill interest while out.
The record
The play against buying and holding ISRG over exactly the same dates, after costs.
| Play, since 2005 | Hold, since 2005 | Play, 5 yrs | Hold, 5 yrs | |
|---|---|---|---|---|
| Annual return | +15.7% | +23.4% | −0.9% | +5.3% |
| Total return | +2,261% | +9,396% | −4% | +29% |
| Worst drawdown | −56.2% | −75.9% | −44.8% | −49.9% |
| Volatility | 33.1% | 39.7% | 25.7% | 34.6% |
| Sharpe ratio | 0.55 | 0.68 | −0.05 | 0.21 |
| Time invested | 73% | 100% | ||
| Switches per year | 1.3 | 0 |
Every call, graded
Right on 13 of 29 closed calls (45%). In calls averaged +31.5%; out calls saw ISRG move +13.0% on average.
| Called | Call | Price | Until | ISRG moved | Result |
|---|---|---|---|---|---|
| Apr 30, 2026 | OUT | $457.61 | now | −7.8% | open |
| Mar 31, 2026 | IN | $460.99 | Apr 30, 2026 | −0.7% | ✕ wrong |
| Jan 30, 2026 | OUT | $504.22 | Mar 31, 2026 | −8.6% | ✓ right |
| Dec 31, 2025 | IN | $566.36 | Jan 30, 2026 | −11.0% | ✕ wrong |
| Aug 29, 2025 | OUT | $473.30 | Dec 31, 2025 | +19.7% | ✕ wrong |
| Dec 29, 2023 | IN | $337.36 | Aug 29, 2025 | +40.3% | ✓ right |
| Nov 30, 2023 | OUT | $310.84 | Dec 29, 2023 | +8.5% | ✕ wrong |
| Apr 28, 2023 | IN | $301.22 | Nov 30, 2023 | +3.2% | ✓ right |
| May 31, 2022 | OUT | $227.64 | Apr 28, 2023 | +32.3% | ✕ wrong |
| May 29, 2020 | IN | $193.34 | May 31, 2022 | +17.7% | ✓ right |
| Mar 31, 2020 | OUT | $165.07 | May 29, 2020 | +17.1% | ✕ wrong |
| Oct 31, 2019 | IN | $184.32 | Mar 31, 2020 | −10.4% | ✕ wrong |
An in call is right when the price rose before the next call; an out call is right when it fell. The latest 12 of 30 calls shown.
How the play works
- In at month-end when the return from 12 months ago to 1 month ago is above zero.
- Out when it is zero or below.
Jegadeesh and Titman ranked thousands of stocks and bought the winners. Testing one stock against zero is time-series momentum, a related idea.
The skip-a-month form came later; their 1993 paper skipped at most a week.
The case against
Valeriy Zakamulin tested moving-average timing on up to 155 years of U.S. stock data and found no statistically significant edge in the second half of that record. The rules earned their keep in a few severe bear markets and lagged buy and hold for long stretches in between.