The High‑Low Index (sometimes called the high‑low breadth indicator) measures how many stocks are hitting 52‑week highs relative to those hitting 52‑week lows and then smooths that ratio with a short moving average. Traders and investors use it as a breadth tool to confirm the direction and strength of a broad market trend (for example, the S&P 500).
Source: Investopedia — (accessed 2025‑10‑06)
How the High‑Low Index is calculated
1. Compute the Record High Percent (for a single day)
Record High Percent = (New Highs) / (New Highs + New Lows) × 100
• If 120 stocks make new 52‑week highs and 80 make new 52‑week lows:
Record High Percent = 120 / (120 + 80) × 100 = 60%
2. Smooth that series with a short moving average (commonly 10 days)
• High‑Low Index = 10‑day moving average of the daily Record High Percent values
• Some traders also use 5‑, 20‑ or other lengths depending on their time frame.
Interpreting the index
• Above 50: more stocks are making 52‑week highs than 52‑week lows → generally bullish.
– Below 50: more stocks are making lows than highs → generally bearish.
– Readings above ~70: market is very strong (trend may be overbought/extreme).
– Readings below ~30: market is very weak (downtrend/extreme selling).
– Sustained extreme readings can persist during strong trends; extremes are not necessarily immediate reversal signals.
Practical trading uses and rules
1. Trend confirmation (primary use)
• Use the High‑Low Index to confirm the direction of the broader market. For example, favor long trades when the index is above 50 and short/bearish strategies when it is below 50.
2. Moving‑average crossover signals
• Many traders add a signal line (e.g., a 20‑day moving average of the High‑Low Index).
• Buy signal: High‑Low Index crosses above its signal moving average.
• Sell signal: High‑Low Index crosses below its signal moving average.
3. Filter with other indicators (to reduce false signals)
• Volume: confirm broad participation on breaks.
• RSI or momentum: require RSI > 50 for bullish confirmation (RSI = 0–100 scale).
• Market breadth measures: advancing/declining issues, AD line, or new highs/new lows counts.
4. Use as a bias tool
• If index > 50, bias toward long setups only; if < 50, bias toward short setups or protect longs.
5. Risk management and execution
• Always use stop losses; consider position sizing based on volatility.
• Avoid trading solely on the High‑Low Index — combine with price structure (support/resistance) and a plan for entries/exits.
• Backtest the chosen parameters and signals on historical data before live trading.
Step‑by‑step: How to calculate and use the High‑Low Index (practical)
1. Collect daily exchange data:
• Count the number of stocks that made new 52‑week highs (New Highs) and new 52‑week lows (New Lows) for each trading day.
2. For each day compute:
• Record High Percent = New Highs / (New Highs + New Lows) × 100
3. Maintain a rolling 10‑day average of those daily percentages:
• High‑Low Index = average of the last 10 Record High Percent values
4. Apply interpretation and rules:
• If the 10‑day average crosses above 50 and is rising, consider a bullish stance.
• If the index crosses below 50 or below its signal MA, consider caution/defensive stance.
Example (simple numeric illustration)
• Suppose 10 daily Record High Percent values over the last 10 days are:
60, 62, 58, 55, 57, 59, 61, 63, 65, 67
– Sum = 607 → 10‑day average = 60.7
– High‑Low Index = 60.7 → above 50 and rising → bullish confirmation
Limitations and cautions
• Can be noisy day‑to‑day; smoothing is necessary.
– During strong trends, the index may remain at extreme levels for a long time — extremes are not guaranteed reversal points.
– Large caps or a small subset of stocks can drive headline market indices even when breadth is weak; the High‑Low Index helps reveal breadth but should be combined with other breadth indicators.
– Data quality and definitions (which universe of stocks is counted) matter — use a consistent data source.
Tips and best practices
• Use the High‑Low Index as one component of a broader decision process — not as a stand‑alone trigger.
– Combine with volume and price action, and confirm with another breadth metric (advancers/decliners, AD line).
– Experiment with smoothing lengths (10‑day is common) and signal lines (20‑day MA) and backtest on your target market.
– Monitor extremes for divergence: if price makes new highs while the High‑Low Index weakens, that can warn of narrowing participation.
Further reading / sources
• Investopedia: High‑Low Index — (accessed 2025‑10‑06)
Summary
The High‑Low Index measures the balance between stocks making 52‑week highs and lows, smoothed with a short moving average. Readings above 50 typically signal bullish breadth, below 50 bearish breadth. Traders use the index for trend confirmation, crossovers against a signal MA for timing, and as a bias filter — always combined with other indicators, sound risk management, and backtesting.