Relative strength ranking answers a simple question: of all the stocks or ETFs I could own, which have been the strongest lately? It is the engine behind many momentum and rotation strategies.
What relative strength ranking is
Relative strength compares the performance of one asset with others, or with a benchmark, over the same period. Ranking puts every asset in a universe in order from strongest to weakest, so a strategy can focus on the leaders.
Relative strength is not RSI
The names are easy to confuse. The Relative Strength Index (RSI) is an oscillator that measures the speed of an asset’s own recent price changes on a 0 to 100 scale. It does not compare one asset with another. Relative strength ranking does.
| Relative strength ranking | RSI | |
|---|---|---|
| Compares | An asset with other assets | An asset with its own recent moves |
| Output | A rank or percentile within a universe | A value from 0 to 100 |
| Typical use | Choosing which assets to hold | Spotting short-term overbought or oversold moves |
How to calculate a relative strength ranking
- Choose a universe, such as a stock index or a list of sector ETFs.
- Calculate each asset’s total return over a lookback, often 3, 6 or 12 months.
- Optionally blend several lookbacks, for example an average of 3, 6 and 12 month returns.
- Sort from highest to lowest and assign ranks or percentiles.
Ways to use relative strength in a strategy
- Selection: hold only the top-ranked assets.
- Filtering: skip any trade signal on an asset ranked in the bottom half.
- Rotation: rebalance on a schedule into the current leaders.
Limitations
Relative strength tells you what has been strong, not what will be strong. Leaders can reverse quickly, rankings can churn in choppy markets, and a whole universe can fall together, in which case the top-ranked asset is simply the one falling least. Pairing ranking with an absolute trend filter helps with that last problem.
Relative strength versus a benchmark
Ranking assets against each other is one form of relative strength. Another compares each asset with a benchmark, such as the S&P 500. You divide the asset’s price by the benchmark’s price and watch the resulting ratio line. When the line rises, the asset is outperforming the benchmark. When it falls, the asset is lagging. This view is useful for answering a different question: not which asset is strongest in the group, but whether a particular stock or sector is beating the market at all.
Both views can work together. A strategy might rank a list of sector ETFs to find the leaders, then only hold the leaders whose ratio line against the S&P 500 is also rising.
Choosing the lookback
The lookback period shapes the whole strategy:
- Short lookbacks of one to three months react quickly to new leadership but produce more turnover and more false signals.
- Medium lookbacks of around six months are a common compromise.
- Long lookbacks of nine to twelve months are steadier but slower to move out of fading leaders.
Many traders skip the most recent few weeks, because very short-term returns tend to partially reverse. Blending several lookbacks reduces the risk of depending on a single setting that happened to work well in the past.
Relative strength in different universes
The same ranking method behaves differently depending on what you rank. With sector or asset class ETFs, it becomes the core of a rotation strategy. With individual stocks, it becomes a momentum selection method. Holding count, overlap, and rebalance rules determine the concentration and trading workload in either case. Whichever universe you choose, define it in advance and keep it consistent, so the ranking is not quietly influenced by hindsight.
Combining ranking with trend signals
Relative strength tells you which assets are leading. It does not tell you whether the market as a whole is rising. In a broad decline, the top-ranked asset can still be losing money. An absolute trend rule adds a separate entry condition: for example, only hold a top-ranked asset if it also trades above its long-term average, or if a moving average crossover on the asset is positive. Compare the ranking-only version with the filtered version to see what the added rule contributes.
Testing a relative strength strategy
- Use data that includes delisted symbols, especially for stock universes, to avoid survivorship bias.
- Include trading costs, because ranking strategies rebalance regularly.
- Test several lookbacks and holding counts, not just the best combination.
- Check results across different market regimes, including sharp reversals, when leadership often changes suddenly.
Questions to ask before using a ranking
- Is the universe fixed in advance, or am I adding recent winners?
- How often does the top group change, and what does that cost in trades?
- What does the strategy hold when everything in the universe is falling?
- Do the results survive a different lookback or holding count?
Use Portfolio Boss’s ranking engine
Ranking is a core PB feature. The Ranking Panel lets you combine rules and set their weights. The Impulse Score rule, for example, ranks instruments by their percentage price gain over a chosen period.
You can rank a stock or ETF universe, apply buy filters, and hold the top qualifying names. PB’s machine learning can search for ranking rules together with buy and sell rules, so you don’t have to choose the whole combination by hand. That’s different from Strategy Mill, which builds and filters separate strategy candidates across a symbol list.
Portfolio Boss founder Dan Murphy began trading in 1997. He built PB around turning research into practical rules and reducing repetitive work. Ranking, strategy discovery, and portfolio management are parts of that same process.
Put your next idea to the test, free
Start with Evo’s strategy builder, then explore PB’s broader ranking and portfolio tools. Portfolio Boss Evo is 100% free for life for the first 100,000 signups ($1,999 value). Download now. Advanced modules are paid.
Backtested and hypothetical results have limitations and do not guarantee future results.
