--- title: "AAII Bull-Bear Spread: Formula, Meaning" description: "The difference between the percentage of bullish and bearish respondents in the weekly AAII Investor Sentiment Survey. It collapses the three-way survey..." canonical: https://www.getswoopr.com/indicators/sentiment/aaii-bull-bear-spread/ source: "Swoopr Investment: https://www.getswoopr.com" --- ## Direct Answer > AAII Bull-Bear Spread is a sentiment measure used to measure positioning, derivatives demand, leverage, or crowd/risk sentiment. The production page must define the exact calculation convention before interpreting higher or lower readings, because platform and provider implementations can differ. # AAII Bull-Bear Spread: Formula, Meaning, Signals, Examples and How to Use It ## How Is AAII Bull-Bear Spread Calculated? The difference between the percentage of bullish and bearish respondents in the weekly AAII Investor Sentiment Survey. It collapses the three-way survey into one signed number. **Formula:** `Spread = bullish % - bearish %` **Inputs:** - AAII bullish percentage - AAII bearish percentage **Worked example.** If 28 percent of respondents are bullish and 45 percent are bearish, the spread is -17.0 percentage points. The inputs are illustrative numbers, not market data. **Reading it.** A positive spread means optimists outnumber pessimists, and a negative one means the reverse. Analysts compare it with its own history; a deeply negative spread is often read as stretched pessimism and a very high one as stretched optimism, both from a contrarian view. **Limits.** The neutral group is ignored, so a spread of zero can come from 33/33/33 or from 10/80/10. The survey is of AAII members and reflects opinion, not what they actually hold. ## Indicator overview | Attribute | Value | | --- | --- | | Category | Sentiment | | Asset classes | Stocks, Indexes, Options, Futures, Macro | | Output type | Ratio/index/scalar | | Parameters | Varies by implementation; document exact settings on use | ## What is AAII Bull-Bear Spread? AAII Bull-Bear Spread is a sentiment measure used to measure positioning, derivatives demand, leverage, or crowd/risk sentiment. The production page must define the exact calculation convention before interpreting higher or lower readings, because platform and provider implementations can differ. For Swoopr, the canonical profile separates definition, calculation, interpretation and decision use. That keeps readers from collapsing a descriptive metric into a trading strategy. An indicator can describe trend, momentum, volatility, participation, positioning or risk without providing a complete entry, exit, sizing or portfolio decision. ## What does it measure? AAII Bull-Bear Spread measures specific market properties in the Sentiment domain. The practical value is repeatability: the same inputs and formula can be applied across a defined dataset, allowing users to compare readings through time or across instruments when the calculation convention is held constant. ## How to read AAII Bull-Bear Spread Interpretation depends on the market property being measured. A descriptive reading is not automatically predictive. The same numerical state can lead to different outcomes in a strong trend, quiet range, event-driven gap or illiquid market. Always combine with context from price structure, volume, and broader market regime before drawing conclusions. ## Strengths - One signed number puts bullish and bearish shares on a single axis, so the sign immediately shows which camp is larger. - Subtracting the two shares sets the neutral group aside, giving a direct measure of net optimism among those with a view. - Reproducible when the formula and data convention are fixed. ## Weaknesses and limitations - A move in the spread can come from either side changing, and the number does not reveal which one moved. - A week-to-week change is measured on a sample of survey responses, so sampling variation alone can move it. - Correlated indicators can create false confidence by repeating the same underlying information. ## Editorial and risk note This page is educational content, not individualized investment advice. It should not imply guaranteed prediction, accuracy or outperformance. Where multiple valid definitions exist, Swoopr states the alternatives and the reason for selecting its primary convention. ## Frequently Asked Questions Is AAII Bull-Bear Spread a buy or sell signal? No. A positive spread means optimists outnumber pessimists, and a negative one means the reverse. The neutral group is ignored, so a spread of zero can come from 33/33/33 or from 10/80/10. A trade built on it still needs a trigger, an invalidation rule, a position size and realistic execution assumptions. What is the best setting for AAII Bull-Bear Spread? AAII Bull-Bear Spread is computed from AAII bullish percentage; AAII bearish percentage, so the choices that matter are the data convention and the window it is read over. Test those across instruments, regimes and out-of-sample periods instead of fitting one historical winner. Can AAII Bull-Bear Spread be used by itself? The neutral group is ignored, so a spread of zero can come from 33/33/33 or from 10/80/10. The survey is of AAII members and reflects opinion, not what they actually hold. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone. Does AAII Bull-Bear Spread work on every timeframe? The calculation (Spread = bullish % - bearish %) can be run on any bar size, but behavior is not portable: a reading on a five-minute chart describes a very different market window from the same reading on a daily chart. Validate the exact timeframe before relying on it. Why does AAII Bull-Bear Spread give false signals? A move in the spread can come from either side changing, and the number does not reveal which one moved. A week-to-week change is measured on a sample of survey responses, so sampling variation alone can move it. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated. How should AAII Bull-Bear Spread be backtested? Rebuild AAII Bull-Bear Spread from AAII bullish percentage using point-in-time data, write the rules before testing, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample and compare with a simpler baseline. ## References - [AAII: AAII Investor Sentiment Survey](https://www.aaii.com/sentimentsurvey) S Swoopr Editorial Team The Swoopr Editorial Team produces independent investment education, research, and tools for understanding markets, evaluating opportunities, and managing risk. All content is educational only and does not constitute personalized investment advice. See our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/).