What it is
The 200-day trend rule is the simplest systematic strategy that has any claim to usefulness: be invested when price is above its 200-day (or 10-month) moving average, and be in cash or short-term bonds when it is below. It is not a return-enhancement strategy. Over long histories its compound return has been similar to buy-and-hold, sometimes slightly lower; what it has changed is the depth of the worst drawdowns. That is the honest pitch: comparable returns, shallower holes, at the cost of many small whipsaw losses and periodic underperformance.
The logic
Bear markets are not single-day events; they unfold over months, with most of the damage occurring after the index has already fallen through a long-term average. A trend rule does not predict the bear market; it recognises one that has started and reduces exposure while it continues. The rule also captures the empirical fact that volatility is higher below the average than above it, so the periods it removes are the ones with the worst risk-adjusted returns.
On the other side are buy-and-hold investors and dip buyers who add exposure during the decline. Over a full cycle they are not wrong; they simply accept a deeper drawdown for the same destination. The trend follower is paying an insurance premium (the whipsaws) for a smoother ride.
Setup rules
- Market: broad equity index funds are the standard; the rule also works, with more whipsaws, on commodities, sector ETFs and bonds. Single stocks are noisier and the rule works less well.
- Timeframe: daily data, evaluated on the last trading day of each month. Daily evaluation triples the number of whipsaws for little benefit.
- Signal: month-end close above the 200-day (or 10-month) simple moving average means invested for the next month; below means in cash or treasury bills.
- Filter (optional): require the close to be more than 1 percent beyond the average before switching, to reduce churn near the line.
- No discretion: the rule is only useful if it is followed at the exact moments it feels wrong, which are the moments it is doing its job.
Entry, stop, target
There is no per-trade stop or target. The "stop" is the next month-end close below the average, which historically occurs 5 to 10 percent below the peak in a typical decline and much further in a crash. The "target" is nothing; the rule holds until it does not.
| Item | Value | Notes |
|---|---|---|
| Instrument | Broad index ETF | Total-return basis |
| Signal | Month-end close vs 10-month SMA | One decision per month |
| Typical whipsaw loss | 2 to 5 percent | Buy above, sell below, one month later |
| Typical whipsaws per decade | 8 to 15 | Concentrated in sideways years |
| Typical drawdown reduction | Half or better in major bear markets | Past results, no guarantee |
| Typical cost | Slight underperformance in strong bull markets | Late re-entry |
A worked R:R is meaningless here; the correct metric is the distribution of drawdowns and the cost of whipsaws across many cycles.
Position sizing and risk
The rule is binary at the instrument level: fully invested or fully out. Position size is therefore set by asset allocation, not by a stop, and the rule should be applied to the risky portion of a portfolio, not to the whole thing. The discussion of portfolio-level risk at /learn/risk-management applies; /tools/position-size is relevant only if you overlay a volatility target. Do not apply leverage to a trend rule to "make up" for the bull-market lag; that converts a drawdown-reducing rule into a drawdown-amplifying one.
What breaks it
- Sideways markets. A year in which the index crosses its average six times produces six small losses and zero benefit. This is the dominant cost and it arrives in most decades.
- Sharp V-bottoms. A crash that recovers within weeks (early 2020 was the recent example) can trigger the exit near the low and the re-entry well above it. The rule loses badly in that case, and there is no fix without giving up its benefit in slow bear markets.
- Taxes. Every switch is a taxable event in a taxable account; after-tax the rule can lag buy-and-hold by more than pre-tax results show.
- Edge decay. The rule's benefit depends on bear markets continuing to be slow. If future declines are faster and recoveries sharper, the rule pays the premium without collecting the insurance.
- Behavioural failure. The most common way this rule fails is that the investor overrides it, usually at the re-entry, because the news is still bad.
How to test it
Get 50 or more years of monthly total-return data for the index (index data extends before any ETF). Compute the rule's return, drawdown, number of switches and time in cash, alongside buy-and-hold. Then repeat for 6, 8, 10, 12 and 15-month averages; the results should be similar, and if only the 10-month version works, that is a warning. Then test on other markets and other countries; a real effect shows up broadly. Fifty years is still only a handful of bear markets, so treat the drawdown numbers as illustrative rather than statistical. See walk-forward-testing.
Variations
- Dual momentum: adds a relative-strength choice between assets; see dual-momentum.
- Multi-asset trend: apply the rule separately to equities, bonds, real estate, commodities and gold, and hold the equal-weighted result.
- Volatility-targeted version: scale exposure inversely to recent realised volatility rather than switching all-or-nothing.
Further reading
moving-average, golden-cross, trend, max-drawdown, whipsaw, etf, index, volatility, backtesting, hindsight-bias.
Related playbooks: dual-momentum, relative-strength-rotation, rebalancing-bands, systematic-momentum-rules