Calculate three measures from the same counts
Let H count new highs, L count new lows and N count all eligible issues with valid classifications for the observation. Every security gets one vote in each applicable count, regardless of market capitalization. StockCharts calls H - L Net New Highs and the universe-normalized version High-Low Percent. Keep H and L visible because subtraction can hide substantial activity on both sides.
- These are different scales. StockCharts defines its High-Low Index as a 10-day simple moving average of Record High Percent. A label containing high-low does not identify the formula by itself.
- For N greater than zero and H and L each between zero and N, normalized net breadth lies between -100% and +100%. A reading outside this range indicates invalid counts, mismatched units or an incorrect denominator.
- If H = L = 0 and N is valid, net breadth is zero and normalized breadth is 0%. Record High Percent is undefined because its denominator is zero; do not replace it with 50%.
- If N is zero or a required count is missing, report unavailable. Missing is not a genuine count of zero.
| Measure | Formula | What the denominator means |
|---|---|---|
| Net new highs | H - L | No denominator; the result is a number of issues. |
| Normalized net breadth | 100 × (H - L) / N | All eligible, valid issues in the same universe. |
| Record High Percent | 100 × H / (H + L) | Only high/low counts; this excludes issues at neither extreme. |