Ultimately, layering and separation, when used in the right circumstances, create an effective design. Layering and separation help minimize and eliminate messy and undecipherable information. Layering especially helps reduce clutter and improves data visually. On page 60, Tufte says that the "layering of data, often achieved by felicitous subtraction of weight, enhances representation of both data dimensionality and density on flatland." So by layering, one can reduce the amount of "weight" and that makes the data visually appealing and easier to read.