Name derived from TRading INdex. Also known as an ARMS index. The index is usually calculated as the number of advancing issues divided by the number of declining issues. This, in turn, is divided by the advancing volume divided by the declining volume. If there is considerably more advancing volume relative to declining volume this will tend to reduce the index (i.e. increase the denominator). Hence, a value less than 1.0 is bullish while values greater than 1.0 indicate bearish demand. The index often is smoothed with a simple moving average.
Copyright © 2011 Campbell R. Harvey, Professor of Finance, Fuqua School of Business at Duke University