Index of Retail Saturation gives one a sense of whether an area is over stored, under stored, or is saturated. In other words, is there room for another competitor. One must always use the square footage of the proposed store in the calculation. Always know the time from of the dollar spent as it could be weekly, monthly, annually or any other time frame. Population 50,000 Average dollar spent per month $30 Square footage for each store including your proposed store..4,000 + 6,000 + 9,000