A market momentum indicator that subtracts the declining issues from the advancing issues on the New York Stock Exchange. This information is used to determine the strength of the market on a daily basis. It is usually smoothed to make it an overbought and oversold indictor. Strong up days show readings of more than +1,000 and weak days have readings of less than -1,000. The difference between the number of advancing and declining issues is the basis of many market breadth indicators. These include the Advance Decline Line, Advance Decline Ratio, Absolute Breadth Index, Breadth Thrust, McClellan Oscillator and Summation Index.