Advance decline line

Also known as the breadth of market indicator, this plots the number of share prices that rise minus the number of share prices that fall over a specific period (usually a day or a week) for a given stock market average (the S&P 500 INDEX, for example). Followers of technical analysis use this to gauge the strength of a stock market. In particular, if the advance-decline line shows a negative return (that is, more shares fall than rise) yet the stock market index continues to rise, they see this as an indication that the market is weak and as a prelude to a fall in the index.