It's a tough start to the week for stocks, as the S&P has its worst day since early August, and the Nasdaq slides more than 1 percent for its worst session since July. But for technician Carter Worth of Sterne Agee, what's more surprising is the recent strength of Nasdaq, as it has come even as the breadth of the market has shrank, with the average Nasdaq stock badly underperforming the index as a whole.
In fact, for that reason, Worth sees the current weakness as merely the beginning of a larger correction.
First, the technician points out the mean stock in the Nasdaq 100 has risen a lot less than the index as a whole—and the median stock has risen even less than that.
"This is the story of the market," Worth said Friday on CNBC's "Options Action." "It's being skewed by a few big names."
Visually, Worth shows this by taking a chart of the index, and comparing it to a chart comparing the number of stocks that are advancing to the number that are declining (commonly known as the "advance/decline line").