The Y-axis represents accumulation, starting from the start date of the selected period.Basically, each day is a step up or down based on net volume. For example, if the net volume for a day is +100 shares (150 shares bought and 50 shares sold), we will see a step up for that day.So, if for five consecutive days, the net volume is +100 shares each day, we’ll see five steps up, reaching a total of +500 shares. Conversely, if a broker sells more than they buy, we’ll see negative steps.
In this case, the purple line represents collective accumulation or accumulation by a group, where we sum up all net volumes for all brokers and treat them as a single "synthetic" broker.What we see on the chart is that investment banks were selling as a group until February 26. Then, their net volume turned positive day after day, meaning they now hold more shares than they did on February 26.
I hope this answers your question!
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