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Arms Index (TRIN)


The Arms Index, also known as TRIN (Trading Index), is a financial indicator used by technical analysts to forecast market price trends. It is calculated by dividing the Advance-Decline Ratio by the Advance-Decline Volume Ratio. A result greater than 1.0 indicates bearish sentiment, while a result less than 1.0 suggests bullish sentiment.


The phonetics of the keyword “Arms Index (TRIN)” would be: R m z I n d e k s (T R I N).

Key Takeaways

<ol><li>Arms Index, also known as TRIN (Trading Index), is a volume-based indicator introduced by Richard Arms in the 1970s. It’s a measure of market strength or weakness, based on the ratio of advancing stocks to declining stocks, compared to the volume of advancing to declining stocks.</li><li>The Arms Index is used primarily to gauge the overall sentiment of the market. When the TRIN value is below 1, it implies that the market’s volume is bias towards advancing stocks. This is generally interpreted as bullish behavior. Conversely, when TRIN is above 1, it means that the market’s volume leans towards declining stocks, indicating bearish sentiment.</li><li>One key takeaway is that despite its usefulness in measuring market sentiment, the Arms Index isn’t recommended as a standalone tool for trading decisions. It is best used in conjunction with other market indicators. Therefore, it should be seen as a part of a larger toolkit for market analysis.</li></ol>


The Arms Index, also known as TRIN (Trading Index), is a crucial tool in business/finance as it offers insights into market strength and breadth, helping investors make more informed decisions. It is a volume-based indicator that determines the relative strength of advancing stocks to declining ones and assesses the overall market sentiment. A value less than one signals that buying pressure is dominating, suggesting a bullish market, while a value greater than one indicates stronger selling pressure, hinting at a bearish market. Being aware of the Arms Index can therefore significantly aid in understanding market trends and underpinning future market movements, leading to potential lucrative investments.


The Arms Index, also known as TRIN (Trading Index), serves a crucial purpose in the world of finance as a valuable indicator for gauging overall market sentiment. It is a volume-based metric that investors and traders use to assess the relative strength of advances and declines in a market, providing insight into possible future movements. Richard W. Arms Jr. developed it in the late 1960s to measure the balance between market supply and demand, making it a crucial tool for short-term trading analysis.Traders use the Arms Index to identify potential signs of market reversal, with extreme readings often suggesting excessive optimistic or pessimistic sentiment. For instance, a TRIN reading above 1.0 is typically interpreted as bearish, suggesting more volume is moving into declining stocks and therefore, a downward turn in the market. Conversely, a reading below 1.0 is viewed as bullish, meaning more volume is flowing into advancing stocks, signaling that the market is steering upwards. By helping traders see behind price movements to the underlying demand and supply dynamics, the Arms Index aids in the development of timely and more informed trading decisions.


1. Stock Market Trading: During a typical day in the stock market, traders frequently use the Arms Index (TRIN) as a technical analysis indicator to assess the overall market condition. For example, if the TRIN ranges 0.5-1.0, traders interpret it as a bullish market and consider it as an opportunity to buy. Conversely, if the TRIN value is greater than 1.5, it indicates a bearish market, suggesting it might be the right time to sell stocks.2. Black Monday, 1987: On Black Monday, October 19, 1987, stock markets around the world crashed. On the New York Stock Exchange, the TRIN spiked up above 2, indicating an overwhelming number of selling volume as compared to buying volume. This extreme reading suggested a bearish market and alerted traders to the impending crash.3. Coronavirus Pandemic Impact in 2020: The stock market experienced a significant fluctuation due to the outbreak of Covid-19. During the major market sell-offs in March 2020, the TRIN reached high levels, showing a significant selling pressure. This provided vital information to traders, portfolio managers and hedge fund managers about the intensity of the sell-off, helping them to manage their investment strategy accordingly.

Frequently Asked Questions(FAQ)

What is Arms Index (TRIN)?

Arms Index, also known as TRIN, is a technical analysis indicator that compares advancing and declining stocks to advancing and declining volume. It determines market strength and breadth, offering insights about overall market sentiment.

How is the Arms Index calculated?

The calculation for TRIN is (Advancing Stocks/Declining Stocks) / (Advancing Volume/Declining Volume).

How should I interpret the Arms Index values?

An Arms Index value less than 1.0 indicates bullish demand, as more volume is flowing into advancing stocks. A value greater than 1.0 signals bearish demand, with more volume flowing into declining stocks.

Is Arms Index used for long-term or short-term analysis?

Usually, the Arms Index is used as a short-term trading tool. However, it can be averaged over multiple days to analyze longer-term trends.

Does a high TRIN value always indicate a bearish market?

Not necessarily, a high TRIN value does show bearish sentiment, but it can also indicate an oversold market condition which might lead to a market reversal.

How reliable is the Arms Index as an indicator of market trends?

The Arms Index is one tool among many. Like any other market indicators, it has its strengths and weaknesses and should be used in combination with other tools and indicators for more accurate prediction.

Where can one find the data necessary to calculate the Arms Index?

The necessary data to calculate the Arms Index is typically found on financial market websites or platforms that provide comprehensive stock market data, such as the New York Stock Exchange.

Related Finance Terms

  • Market Indicator
  • Advance/Decline Ratio
  • Volume Ratio
  • Short-Term Trading Index
  • Market Volatility

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