In this video, I show you how to resize marks (in this case circles) dependent on how many marks are in the view. For example, if all possible marks are in the view (100%), the circles should be small. If only 10% of possible marks are in the view, the circles should be large.

I show how to do this on a map, but it can be extended to scatter plots, box plots, dot plots, jittered bar chart, and more.