What it is
Relative strength (RS) rotation ranks a universe of sectors, industries or stocks by their performance relative to a benchmark over a lookback window, holds the top few, and re-ranks on a schedule. It is momentum applied across assets rather than within one. The "sector rotation" framing comes from the observation that leadership moves through the economy in phases, but the playbook does not require you to predict which phase comes next; it just follows what is already leading.
The logic
Capital flows are slow. When a sector begins to outperform, the flow into it from funds and allocators unfolds over months, not days. Relative strength captures that persistence. It also exploits the behavioural fact that most investors under-react to changes in a sector's fundamentals and over-react at the end, which produces trends in relative performance that last longer than they "should".
On the other side are value-oriented investors selling leaders because they look expensive, and contrarians buying laggards. Over a 3 to 12-month horizon, momentum has historically beaten them on average; over 3 to 5 years it has not, and that is why the playbook rotates.
Setup rules
- Market: sector and industry ETFs (the simplest), or a universe of 100 to 500 liquid stocks. Not micro caps.
- Timeframe: daily data, monthly decisions.
- Ranking: the average of 3-month and 6-month total return minus the benchmark's return over the same windows. Skipping the most recent month helps in stocks (short-term reversal) and matters less in ETFs.
- Hold rule: hold the top 3 of 11 sectors, or the top 10 percent of the stock universe; equal weight.
- Rotation rule: re-rank on the first trading day of each month; sell anything that has dropped out of the top 5 sectors (or top 20 percent of stocks); buy the new leaders. A buffer zone reduces turnover.
- Regime filter: if the benchmark index closes the month below its 10-month (roughly 200-day) average, hold cash or short-term treasuries instead of the leaders. This one rule is what keeps the strategy alive through bear markets.
Entry, stop, target
There is no chart-based entry; the trade is a monthly rebalance at the open. Individual positions have no fixed stop, but the rotation rule acts as one: a leader that falls to the middle of the ranking gets sold. For discretionary traders who want a stop, a 15 percent trailing stop from the highest close is a reasonable overlay.
| Item | Value | Notes |
|---|---|---|
| Universe | 11 sector ETFs | Plus cash as a 12th option |
| Hold | Top 3 | Equal weight, one third each |
| Ranking window | 3 and 6 months | Relative to broad index |
| Rebalance | Monthly | About 3 to 6 swaps per year |
| Typical single-position drawdown | 10 to 20 percent | Before rotation removes it |
| Regime filter | Index below 10-month MA | Move to cash |
A worked R:R does not apply cleanly to a rotation strategy; the relevant numbers are annualised return versus max-drawdown, both of which should be evaluated over decades. Any published number is a backtest, not a promise.
Position sizing and risk
The position size is set by the number of holdings, not by a stop. With three sectors at one third each, a 20 percent sector drawdown is a 6.7 percent portfolio hit. Anyone who needs the risk smaller holds more sectors or adds a volatility-scaling rule. The framework at /learn/risk-management covers portfolio-level risk, and /tools/position-size can be used for the trailing-stop overlay if you add one. Rotation strategies are concentrated by design; do not add leverage to compensate for a slow month.
What breaks it
- Momentum crashes. When a bear market reverses sharply, the laggards rally hardest and the leaders lag for months. The regime filter helps, but the turn from cash back into leaders is always late.
- Whipsaw around the regime filter. A sideways year with the index crossing its 10-month average repeatedly produces several small losses and a lot of turnover.
- Costs and taxes. Monthly rotation produces short-term capital gains and 30 to 60 percent annual turnover; after-tax results can be materially lower than pre-tax backtests.
- Edge decay. Cross-sectional momentum is one of the most studied effects in finance, and the excess return has narrowed as capital has crowded in. It has not vanished, but the drawdowns have not shrunk with the returns.
- Long flat periods. Expect multi-year stretches of underperforming a plain index fund.
How to test it
Use total-return data (dividends included) for at least 20 years, with the ETF's underlying index history filling in years before the ETF existed. Simulate monthly rebalances with realistic costs and a one-day execution lag. Report compound return, max-drawdown, worst 12-month period, turnover and the number of months in cash. Run the test with several lookback windows (3, 6, 9, 12 months) and several hold counts; if the results only look good for one combination, the edge is a fitting artefact. See walk-forward-testing for the protocol. Two decades of monthly data is only 240 decisions, so treat any Sharpe ratio above 1 with suspicion.
Variations
- Dual momentum: adds an absolute-momentum test to the relative one; see dual-momentum.
- Stock-level RS with a 12-1 month lookback; see systematic-momentum-rules.
- RS as a filter for discretionary breakouts and pullbacks, only trading names in the top RS quartile.
Further reading
sector-rotation, etf, index, correlation, max-drawdown, sharpe-ratio, diversification, risk-on-risk-off, backtesting, survivorship-bias.
Related playbooks: dual-momentum, systematic-momentum-rules, base-breakout, ema-pullback-trend