According to Stockcharts,
McClellan Summation Index is a breadth indicator derived the McClellan Oscillator, which is a breadth indicator based on Net Advances (advancing issues less declining issues). The Summation Index is simply a running total of the McClellan Oscillator values.
Here you can see the very obvious bearish trendline that has been tagged twice and nearly another in April, but the Index was so weak it couldn’t muster enough energy to reach it. A MACD crossover and a weakening RSI shows the market internals of the Nasdaq are in bad shape. The tightening of the ATR with the Bollinger Bands narrowing around it suggests a big move is coming one way or the other. You have to give the bears the benefit of the doubt with all the confirming action I point out in the video below.
“High volatility begets low, and low volatility begets high.” ~John Bollinger
