What happens when I leave out empty cells in regression?
When you have empty cells (and by empty cells, I assume that you are referring to a missing value of an observation specific variable), then STATA by default drops the entire row. So in a sense, even when you have a single missing value on a variable and you have say 100 variables, you lose the whole row (the entire observation). This is by default. If you want to avoid this, perhaps think about imputing the missing data points.