American Association of Individual Investors

American Association of Individual Investors

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American Association of Individual Investors
American Association of Individual Investors
Using the Arms Index (TRIN) for Market Breadth Analysis

Using the Arms Index (TRIN) for Market Breadth Analysis

The most reliable signals occur when extreme TRIN readings align with other technical indicators and happen during high-volume sessions.

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AAII
Aug 14, 2025
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American Association of Individual Investors
American Association of Individual Investors
Using the Arms Index (TRIN) for Market Breadth Analysis
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Wayne Thorp leads a class in AAII's new Essential Investing Video Course. Go to https://www.aaii.com/ves for more information and to subscribe.

  • Explains how the TRIN measures market sentiment using advancing/declining stocks and their respective trading volumes

  • Examines historical effectiveness, key limitations and evolving interpretations of the TRIN in modern, algorithm-driven markets

  • Provides practical guidance on using the TRIN alongside other indicators for risk management and short-term sentiment analysis

With markets hitting new highs and volatility lurking around every corner, knowing when sentiment has reached extremes could save your portfolio. The Arms Index, also known as the TRIN (Trading Index), has been measuring market breadth and volume since 1967, catching capitulation points that mark major bottoms. But in today’s algorithm-driven markets, does this classic indicator still work? The answer might surprise you.

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