The Mass Index, created by Donald Dorsey, compares the trading range (High - Low) for each point in the period to try and identify trend reversals. The greater the difference between the High and the Low, the greater the Mass Index; Conversely the smaller the difference between the High and the Low, the smaller the Mass Index is.
Dorsey hypothesized that, when the figure jumps above 27 – creating a “bulge” – and then drops below 26.5, the stock is ready to change course. An index of 27 represents a rather volatile stock, so some traders set a lower baseline when determining the presence of a price bulge.
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