Relative Strength vs S&P 500: Definition, Formula & How UQS Uses It
What Is Relative Strength vs S&P 500?
Relative Strength versus the S&P 500 measures how a stock has performed compared to the broad market benchmark over a defined period, typically the past 3-12 months. If a stock returned 20% while the S&P 500 returned 10%, its relative strength is +10% — it outperformed the market by 10 percentage points. This metric captures the essence of momentum investing: the empirical observation, documented by Jegadeesh and Titman (1993) and confirmed in dozens of subsequent studies, that stocks which outperform the market tend to continue outperforming over subsequent months. The momentum effect is one of the most robust anomalies in financial economics, observed across different countries, time periods, and asset classes. The behavioral explanation centers on underreaction: good news about a company takes time to fully incorporate into the stock price because investors are slow to update their beliefs, creating a drift that produces persistent outperformance. Relative strength versus the index (rather than absolute returns) isolates stock-specific momentum from overall market movements, providing a purer signal.
How Is Relative Strength vs S&P 500 Calculated?
Stock Return is the percentage price change of the individual stock over the measurement period (typically 6 or 12 months, excluding the most recent month to account for short-term reversal effects). S&P 500 Return is the percentage price change of the S&P 500 index over the same period. The difference (excess return) indicates whether the stock outperformed or underperformed the broad market. Positive relative strength means the stock beat the market; negative means it lagged. Some implementations use a ratio (stock return / index return) rather than a difference, but the interpretation is the same: values above 1.0 or above 0% indicate outperformance. The UQS model uses relative strength because it isolates company-specific momentum from market-wide movements — during a broad market rally, even mediocre stocks rise, and relative strength identifies which stocks are rising more than the tide lifts all boats.
How UQS Score Uses Relative Strength vs S&P 500
Relative Strength vs S&P 500 carries a 25% weight in the Momentum pillar, equal to the 52-week range position. Higher relative strength (outperformance vs. the benchmark) scores better. The metric is computed client-side from historical price data. As a PRO-only feature, the Momentum pillar adds a sixth scoring dimension: when enabled, it receives 10% of total UQS weight while the five fundamental pillars scale by 0.90. Relative strength complements the SMA ratio (which measures absolute trend direction) and the 52-week range (which measures proximity to highs) by adding a comparative dimension: a stock can be in an uptrend and near its highs but still underperforming the market, which this metric would flag.
Real-World Example
During periods when NVIDIA dramatically outperformed the broader market (returning, say, 200% while the S&P 500 returned 25%), its relative strength would be +175 percentage points — an extraordinary figure reflecting the stock's dominant performance. This would earn a maximum momentum score. Conversely, a stock like a traditional energy company that returned 5% while the market returned 15% would show -10% relative strength, scoring poorly despite positive absolute returns. The key insight is that relative strength measures whether a stock is winning the race, not just whether it's moving forward. A stock that rises 10% in a market that rises 20% is actually a relative loser, and the momentum evidence suggests it's more likely to continue underperforming than to suddenly catch up.
Frequently Asked Questions
What is relative strength in investing?
Relative strength compares a stock's price performance to a benchmark (usually the S&P 500) over a specific period. It answers the question: is this stock outperforming or underperforming the broader market? A stock with positive relative strength is beating the market; negative relative strength means it's lagging. Academic research consistently shows that stocks with strong relative strength over the past 3-12 months tend to continue outperforming over the next 3-12 months, making it one of the most robust predictive factors in finance. This is not the same as the Relative Strength Index (RSI), which is a separate technical indicator measuring overbought/oversold conditions.
Why does momentum persist in stocks?
Momentum persists primarily due to behavioral biases: investors underreact to new information, causing prices to adjust gradually rather than instantly to their fair value. When a company reports strong earnings, the stock jumps but typically doesn't immediately reach its full fair value — additional gains accrue over the following weeks and months as more investors process the information and update their models. Herding behavior amplifies this: as institutional investors notice a stock outperforming, they allocate more capital, pushing prices further. Additionally, there's a disposition effect where investors sell winners too quickly and hold losers too long, slowing the price discovery process in both directions. These behavioral patterns create the persistent trends that momentum strategies exploit.
Related Metrics
Want to see how all 29 metrics work together?
The UQS Score combines Quality, Moat, Growth, Risk, Valuation, and Momentum into a single composite score for 6,400+ stocks.
Read the Full Methodology