increase = YES

decrease = NO

How we define a "single day change":

If on a Tuesday the market closes at 1000, then on Wednesday it ends it is 1100, that's a 10% change. We don't count within-day changes. And we count close-cose (subsequent closes) rarher than (open-close).

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.