This short-term technical analysis breadth indicator was developed by Richard W. Arms in 1967. The Arms Index, or TRIN (TRading INdex) shows the ratio between the average volume of declining stocks and the average volume of advancing stocks. A rising TRIN is bearish and a falling TRIN is bullish. TRIN is interpreted as the follows: A ratio of 1 means the market is in balance; above 1 indicates that more volume is moving into declining stocks; and below 1 indicates that more volume is moving into advancing stocks. Also referred to as: the Short Term Trading Index, TRIN, MKDS, and STKS.