The Arms Index, also known as the TRIN (Short-Term TRading INdex), was developed by Richard Arms in the 1960s. It is calculated by dividing the ratio of advancing stocks to declining stocks by the ratio of advancing volume to declining volume. Interpreting the Arms Index involves looking at its value in relation to certain thresholds. A value below "1" is considered bullish, indicating that advancing stocks and volume dominate the market. Conversely, a value above "1" is considered bearish, suggesting that declining stocks and volume are more prevalent. Extremely low values (below 0.5) or high values (above 2) are often seen as potential reversal signals.
