I understand adv/dec; however, it's not clear as to what the number represents.  So, for example, yesterday T2100 closed at 13,300.  What does 13,300 actually mean and how is it calculated?

Thanks, Stuart

The T2100 advance decline line is a cumulative indicator in which a value is added or subtracted from that indicator each day. That means the actual value is pretty meaningless. What is of meaning is the relative position of the T2100 advance decline line to past values, ranges and moving averages. You are interested in if the T2100 line is up or down.

T2100 Advance/Decline Line

The Advance Decline Line is a cumulative indicator that is calculated by subtracting the number of declining stocks for the day from the number of advancing stocks for the day. Each day’s calculation is added or subtracted from the previous day’s indicator value.

The Advance/Decline Line from Worden, T2100, represents a great improvement over the common one. T2100 is calculated only from NYSE common stocks and based off of percentages. It is calculated from the percentage of advancing stocks minus the percentage of declining stocks, rather than using raw numbers. For example, if 55% of stocks on the NYSE were up today and 30% of stocks on the NYSE were down, the net change today would be 25 (55% - 30%).

When the Advance/Decline line rises in lock step with a broad average, such as the SP-500, it is an indication that a majority of stocks are in agreement with the strength shown by average. This is called "strong breadth." When the Advance/Decline line and the broad average decline together, breadth is weak. When these two lines disagree, it is called a divergence, and the Advance/Decline line is more apt to be correct, although it is by no means a certainty.