Table of Contents

Relative Strength

The 30-Second Summary

What is Relative Strength? A Plain English Definition

Imagine you're watching a marathon. The most obvious metric is each runner's absolute speed—how many miles per hour they are running. This is like a stock's price going up or down. But what if you wanted to know who was actually winning the race? To do that, you'd compare each runner's performance relative to the others. A runner might be slowing down slightly, but if everyone else is slowing down even more, she is gaining relative strength and pulling ahead of the pack. In the investing world, Relative Strength (often abbreviated as RS) does exactly this. It's not a complex formula locked in a vault on Wall Street; it's a straightforward comparison. It measures how a stock's price has performed against a benchmark, which could be:

A stock with high or improving relative strength is “pulling ahead of the pack.” Its price is rising faster (or falling slower) than the benchmark. A stock with low or worsening relative strength is falling behind. It’s essential to understand that Relative Strength is a cornerstone of a completely different investment philosophy called technical_analysis. Technical analysts focus on charts, patterns, and price momentum, believing that all known information is already reflected in the stock's price. For them, high relative strength is often a “buy” signal. For a value investor, who focuses on a business's underlying worth, it's a very different kind of signal, as we'll see.

“In the short run, the market is a voting machine but in the long run, it is a weighing machine.” - Benjamin Graham

This timeless quote perfectly captures the essence of Relative Strength for a value investor. RS is a printout from the “voting machine”—it tells you which stocks are winning the popularity contest right now. Our job, however, is to use the “weighing machine”—to determine the company's actual substance and intrinsic_value.

Why It Matters to a Value Investor

If Relative Strength is a tool for market technicians and momentum chasers, why should a disciplined value investor even bother with it? Because understanding the “voting machine” is crucial for finding opportunities the crowd has overlooked. For us, Relative Strength is not a tool for buying, but a tool for thinking. Here’s how it fits into a value investing framework:

In short, a value investor uses Relative Strength in the opposite way of a momentum investor. They see strength and get skeptical; we see weakness and get curious.

How to Calculate and Interpret Relative Strength

While sophisticated charting software can plot a Relative Strength line automatically, the concept itself is very simple.

The Method

The most common way to visualize Relative Strength is to create a ratio and plot it on a chart. The Formula: `Relative Strength = Stock Price / Benchmark Price` Let's say you want to compare the performance of a fictional company, “Innovate Corp” (ticker: INOV), to the S&P 500 (represented by the ETF, SPY).

  1. Step 1: On January 1st, INOV is trading at $120 and SPY is at $400.

The RS Ratio is `$120 / $400 = 0.30`.

  1. Step 2: Three months later, INOV has surged to $165, and SPY has risen to $440.

The new RS Ratio is `$165 / $440 = 0.375`.

  1. Step 3: By plotting this ratio over time, you get a Relative Strength Line. Since the ratio increased from 0.30 to 0.375, the RS line would be trending upwards, showing that INOV is outperforming the S&P 500.

For those who prefer simple arithmetic over charts, an even easier method is to compare percentage changes over a set period (e.g., the last year):

  1. INOV annual return: +37.5%
  2. S&P 500 annual return: +10%
  3. Conclusion: INOV has shown strong relative strength.

Interpreting the Result

The interpretation depends entirely on your investment philosophy.

RS Trend Momentum Investor's Interpretation Value Investor's Interpretation
Rising Line “The stock is a winner and the trend is my friend. This is a buy signal.” “The stock is popular and potentially over-hyped. Is the price now far above its intrinsic_value? I must be extra cautious.”
Falling Line “The stock is a loser and underperforming. This is a sell or avoid signal.” “The stock is unpopular. This is my cue to start researching. Is the underlying business still excellent? Has the market overreacted, creating a margin_of_safety?”
Flat Line “The stock is moving in line with the market. No strong signal.” “The stock is performing as expected. No immediate signs of extreme fear or greed to investigate.”

The cardinal sin for an investor is to see a rising RS line and conclude “it must be a good company” or see a falling line and think “it must be a bad company.” The RS line reflects market opinion, not business quality. Your job as a value investor is to find the situations where the two dramatically disagree.

A Practical Example

Let's compare two hypothetical companies over one year, during which the S&P 500 rose by 15%.

^ Metric ^ Flashy AI Solutions (AIZ) ^ Dependable Bolt & Nut (DBN) ^ S&P 500 Benchmark ^

Starting Price $100 $50 $400
Ending Price $220 $52 $460
Price Change +120% +4% +15%
Relative Strength Extremely Strong Very Weak Baseline

The Momentum Investor's View: The momentum investor sees AIZ's chart and is thrilled. The stock is up 120%, crushing the market's 15% return. Its relative strength is off the charts. This is a clear “buy” signal, based on the assumption that this powerful trend will continue. They wouldn't even look at DBN; its 4% return makes it a “laggard” to be avoided at all costs. The Value Investor's View: The value investor looks at this data and a completely different set of questions arise:

The value investor uses Relative Strength not to make a decision, but to decide where to focus their research efforts—typically on the unloved and unpopular.

Advantages and Limitations

Strengths

Weaknesses & Common Pitfalls

1)
Crucially, this is not the same as the Relative Strength Index, or RSI, which is a different tool altogether.