Relative Strength

Relative strength compares two price series. A stock can fall and still show rising relative strength if the index falls more. A stock can rise and show falling relative strength if the index rises faster. This is not the Relative Strength Index. RSI is a bounded oscillator of one instrument's own gains and losses. Relative strength is a comparison. The distinction matters because traders say "RS" and mean either. In a selection system, relative strength is the ranking tool: buy leaders, avoid laggards, on the evidence that outperformance persists for a while more often than a coin flip. Persistence is a tendency with ugly reversals. Leaders become the things that are sold when the regime ends.

Choose the benchmark on purpose. A bank versus the bank index tells you whether it leads its peers. The same bank versus the broad market tells you whether the group is wanted at all. Both are useful and they answer different questions. Use a ratio line or a stated formula, not a squint at two charts in different windows. A breakout in the ratio is often more informative than a small breakout in the stock, because it says the stock is leaving the pack, not just that the pack is being marked up. Require liquidity. The strongest ratio on the board is often a thin stock whose one print will reverse the "leadership" tomorrow.

Use relative strength to build a list, not to time a tick. Prefer long setups in names that are outperforming, and be slower to buy breakdowns in names that are already lagging, unless you deliberately trade laggards. In a market decline, relative strength tells you what to look at first when the market stabilises. It does not tell you to buy them during the decline. Pair the ratio with the absolute trend. A leader in a bear market can still lose money if you are long only the ratio and the ratio rises while price falls. Decide whether you are trading outperformance, which can be a pair, or trading the price, which needs the absolute chart to agree.

Looking at RSI when the conversation is about relative strength, or the reverse. Also ranking by a one-week return and calling it leadership. A short window is a spike. And holding a laggard because the company is familiar, while the ratio has been falling for months. Familiarity is not relative strength. Finally, buying the highest-ranked name on the day it becomes the highest, after a vertical move, with no setup and no room. Rank is not an entry.

Relative strength regimes rotate. Last year's leaders are often next year's sources of cash. A ranking system without a rebalance rule and a turnover budget will chase. The ratio does not include fundamentals, borrow, or the event calendar. A stock can outperform all the way into an earnings gap that erases the outperformance in one print. And in a crisis, relative strength collapses toward "everything fell." The signal is most useful in a differentiated market and least useful when correlations have gone to one.