In 1991, the NYSE switched over to decimal trading which has both increased trading volumes and changed the rate of ascent of the AD Line. Decimalization has increased the likelihood that a stock's close will be up or down on the day. Since aggregate down moves tend to be larger than up moves it means that the upward trend on the AD Line should be steeper, which is what we see. The AD Line is in new high territory and as a result I expect to see the SUM Index make new historic highs over +6000 this year before the market finally peaks.
The chart shows the dates of two NYSE rule changes which
have affected trading volumes and the AD Line.
Click to enlarge