Rising value for advance and decline indicators are often a technical signal of a bullish market while declining values represent a bearish market. In other words, a market will be more bullish if more stocks advance than decline and vice versa over a particular time frame.
There are various technical indicators that are calculated using advances and declines one of which is Advance-decline ratio. It compares the number of stocks that closed higher against the number of those that closed lower during a particular period. A low value of advance-decline ratio can indicate an oversold market, while a high value can signal an overbought market. Either of these conditions could mean that a market trend has become unsustainable and is about to reverse.