# Advance/decline Internals

Also known as: A/D line, A/D ratio, ADD, Absolute Breadth Index, STIX.
A Breadth, Sentiment & External Data concept (Breadth) in the LuxAlgo Library, with 1 indicator implementation.

## What are Advance/decline Internals?

Advance/decline internals are the breadth statistics built from two counts: how many issues on an exchange closed higher (advances) and how many closed lower (declines). The A/D line is the running sum of advances minus declines and is the classic participation gauge. The A/D ratio divides advances by declines for a normalized single-day reading. Net advances (quoted intraday as ADD) is the raw difference. The Absolute Breadth Index takes the absolute value of that difference, measuring how one-sided activity is regardless of direction, and STIX exponentially smooths advances as a share of advances plus declines.

Breadth counting is among the oldest branches of market analysis. Daily tabulations of advances and declines were being kept by the mid-1920s, work commonly credited to Leonard Ayres and his colleagues at the Cleveland Trust Company, and the cumulative A/D line became a fixture of mid-century market commentary. Later analysts built named tools on top of the counts: Sherman and Marian McClellan derived their oscillator and summation index from smoothed net advances in 1969, Norman Fosback introduced the Absolute Breadth Index in the 1970s, and STIX came from the Polymetric Report advisory letter.

These matter because capitalization-weighted indices can be carried by a handful of megacaps while the average stock deteriorates. Internals count every issue equally, so they expose narrowing participation before it shows in price. The standard caveat: breadth warnings can persist for months before price cares, and exchange composition (funds and preferred issues on the NYSE tape) can tint the counts.

In modern practice the counts sit inside a wider internals dashboard. Intraday index traders read net advances alongside the [TICK index](https://www.luxalgo.com/library/concept/tick-index/), which counts stocks upticking versus downticking in real time; position traders pair the A/D line with level-based participation gauges such as the [percentage of stocks above their 20-, 50-, and 200-day averages](https://www.luxalgo.com/library/concept/percent-stocks-above-20-50-200-day-ma/). The counts remain equity-specific: they need a broad reported issue universe, which is why breadth work centers on NYSE and Nasdaq data.

## How to read advance/decline internals on a chart

Breadth is read against the index it describes: plot the internal beneath the benchmark.

1. Load the exchange's breadth series (advancing issues, declining issues, or net advances under symbols such as ADD) or a toolkit study that computes them.
2. Plot the cumulative A/D line under the index and compare swing highs and lows: confirmation means both series printing new extremes together.
3. Mark sessions where the index makes a new high the line fails to match, and track whether that divergence repeats at subsequent highs.
4. For single-day readings, use net advances or the A/D ratio: days where one side overwhelms the other flag potential thrusts or washouts.
5. Note the universe behind the counts: NYSE all-issue data includes funds and preferred shares, so a common-stock-only or index-specific breadth series makes a useful cross-check.

## How it's calculated

Breadth measures built from the counts of advancing and declining issues on an exchange for each session.

```
Net_t = A_t - D_t (net advances, the advance/decline difference, ADD)
ADL_t = ADL_{t-1} + Net_t (the cumulative advance/decline line, seeded at 0 on the first session)
ADR_t = A_t / D_t (the advance/decline ratio)
ABI_t = abs(A_t - D_t) (the Absolute Breadth Index)
PctAdv_t = 100 × A_t / (A_t + D_t)
STIX_t = STIX_{t-1} + 0.09 × (PctAdv_t - STIX_{t-1})

  A_t: number of advancing issues in session t
  D_t: number of declining issues in session t
  t: session (trading day) index
  0.09: STIX smoothing constant (roughly a 21-day EMA)
```

The A/D line's absolute level depends on its start date, so its slope and divergences against price carry the information.

Unchanged issues are excluded above; some variants normalize net advances by total traded issues instead.

ADD usually names the intraday NYSE advance/decline difference updated through the session.

## How traders use it

- As trend confirmation: index highs accompanied by A/D line highs indicate broad participation, while price highs the line fails to confirm set up the classic breadth divergence at index tops.
- As thrust and washout detection: rare stretches where advances overwhelm declines feed breadth-thrust definitions, and deeply lopsided down days mark potential capitulation.
- As raw material: smoothed net advances drive derived tools such as the [McClellan Oscillator](https://www.luxalgo.com/library/concept/mcclellan-oscillator/) and its summation index, so reading the inputs helps sanity-check the derivatives.
- As a volatility cross-check: deteriorating breadth alongside a rising [VIX](https://www.luxalgo.com/library/concept/vix/) or firming [implied volatility](https://www.luxalgo.com/library/concept/implied-volatility/) describes a market losing sponsorship, while breadth weakness volatility ignores may reflect rotation rather than broad distribution.
- As a price-based sanity check: [ratio charts](https://www.luxalgo.com/library/concept/ratio-charts/) of an equal-weight index against its cap-weighted version, or a [relative strength comparative](https://www.luxalgo.com/library/concept/relative-strength-comparative/) line between the two, ask the same participation question using only price.

## Advance/decline internals vs related breadth measures

- **McClellan Oscillator** (https://www.luxalgo.com/library/concept/mcclellan-oscillator/): A derivative: the difference between two exponential moving averages of daily net advances. It converts the raw counts into a momentum-of-breadth reading, and its summation index cumulates that into a slower gauge.
- **TICK Index** (https://www.luxalgo.com/library/concept/tick-index/): A real-time count of NYSE stocks on upticks minus those on downticks. It measures the moment's pressure, while daily advance/decline counts settle the question at the close.
- **% Stocks Above 20/50/200-day MA** (https://www.luxalgo.com/library/concept/percent-stocks-above-20-50-200-day-ma/): Participation measured by level rather than daily change: the share of issues holding above a reference average. It moves more slowly than day-count breadth and answers how many stocks remain in uptrends, not how many rose today.

## FAQ

### What is the difference between the A/D line and the A/D ratio?

The A/D line is cumulative: each day's advances minus declines added to a running total, read for trend and for divergence against the index. The A/D ratio is a single-day snapshot, advances divided by declines, comparable across time because it is normalized. The line answers whether participation is trending; the ratio answers how one-sided today was.

### Is an A/D line divergence a sell signal?

Not by itself. A divergence says fewer stocks are carrying the index, a condition that has preceded some major tops but can also persist for months while price keeps rising. Most practitioners treat it as a warning that raises the bar for new longs and wait for price structure to break before acting on it.

### What is the Absolute Breadth Index?

Norman Fosback's measure of activity without direction: the absolute value of advances minus declines. High readings mark one-sided, high-churn markets; low readings, quiet ones. Fosback read unusually high values as constructive for forward returns, evidence later analysts treat as suggestive rather than settled.

### What is STIX?

A short-term breadth oscillator from the Polymetric Report: an exponential smoothing of advances as a percentage of advances plus declines. It hovers around the low 50s, with customary overbought and oversold zones in the mid-50s and mid-40s.

### What counts as a breadth thrust?

A rare burst of upside participation. The classic definition comes from Martin Zweig: the ten-day exponential average of advances divided by advances plus declines rising from below 0.40 to above 0.615 within ten sessions. Variants exist, but all try to capture the same fast flip from washed-out to overwhelming demand.

### Why is the NYSE A/D line sometimes criticized?

Composition. The all-issue tape includes closed-end funds, preferred shares, and other rate-sensitive listings that are not operating companies, so the line can tilt with interest rates rather than equity demand. Common-stock-only lines and index-specific breadth address the objection, at the cost of shorter histories.

### Do advance/decline internals exist outside stock indices?

Only where a broad universe trades side by side, so there is no direct equivalent for a single pair or coin. Analysts improvise: a [currency strength meter](https://www.luxalgo.com/library/concept/currency-strength-meter/) plays the participation role across forex, and [open interest](https://www.luxalgo.com/library/concept/open-interest/) asks a related but different question about commitment in futures.

## Implementations in the Library

- Market Breadth Toolkit (LuxAlgo): https://www.luxalgo.com/library/indicator/market-breadth-toolkit/

## Related concepts

- Up/down Volume: https://www.luxalgo.com/library/concept/up-down-volume/
- TICK Index: https://www.luxalgo.com/library/concept/tick-index/
- % Stocks Above 20/50/200-day MA: https://www.luxalgo.com/library/concept/percent-stocks-above-20-50-200-day-ma/
- New Highs − New Lows: https://www.luxalgo.com/library/concept/new-highs-new-lows/
- Equal-weight vs Cap-weight Ratio: https://www.luxalgo.com/library/concept/equal-weight-vs-cap-weight-ratio/
- Participation Divergence at Index Highs: https://www.luxalgo.com/library/concept/participation-divergence-at-index-highs/
- TRIN: https://www.luxalgo.com/library/concept/trin/
- McClellan Oscillator: https://www.luxalgo.com/library/concept/mcclellan-oscillator/
- Breadth Thrusts: https://www.luxalgo.com/library/concept/breadth-thrusts/
- Sector Breadth: https://www.luxalgo.com/library/concept/sector-breadth/

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Source: https://www.luxalgo.com/library/concept/advance-decline-internals/ (LuxAlgo Library, the encyclopedia of trading & technical analysis). Free to use with attribution: https://www.luxalgo.com/library/license/