So at the end of the day, we have a total score of transactions occurring on upticks (buying pressure) and a total score of transactions occurring on downticks (selling pressure). What can we learn from these measures?

If we divide the sample from 2012-present into quartiles, we find out that when daily upticks are lowest, the next 10 days in SPY have averaged a loss of -.05%. When daily upticks have been highest, the next 10 days in SPY have averaged a gain of +1.02%. Heavy buying tends to beget further buying. That's a momentum effect.