increase = YES

decrease = NO

How we define a "single day change":

If it ended on say, Tuesday at 1000. And then at end of day Wednesday it is 1050 or higher, that is a >=5% change. Changes within a single day which aren't the closing price are irrelevant.

We take (end of prior day) => (end of day in question) as the change, so that we treat "overnight changes" as being part of the subsequent day.