# How Measure Cannibalization works

The Measure Cannibalization tool calculates the amount of overlap between two or more polygons. This overlap refers to the extent at which polygon boundaries coincide.

With the Measure Cannibalization tool, you can use statistics (returned as attributes) and include them in an optional report to help you assess the cannibalization impact and guide potential trade area revisions. The generated statistics define overlap proportions for the affected trade area polygons. The images below provide an example of how cannibalization statistics are calculated.

Two trade areas, labeled with their Area IDs, are displayed below as light green polygons.

An output feature class is displayed in darker green. This represents the area of overlap between the two trade areas.

The feature attribute table displays the statistics of the dark green (overlap) area.The field definitions are as follows:
• ID—Identifies the trade areas being compared—for example, Store 1 trade area represents A and Store 2 trade area represents B.
• A1—Compares total area of the trade areas being compared. In this case, Store 1 trade area is 93.7 percent as large as Store 2 trade area.
• A2—The proportion of the two trade areas that overlap. In this case, 15.9 percent of the trade areas’ union overlaps.
• A3—The proportion of Store 1 trade area or A that falls within Store 2 trade area or B. In this example, 28.4 percent of Store 1 trade area lies within Store 2 trade area.
• A4—The proportion of Store 2 trade area or B that fall within Store 1 trade area or A. In this case, 26.6 percent of Store 2 trade area lies within Store 1 trade area.
Below, are the same statistics as represented in the optional Measure Cannibalization report.
##### Note:

The information in the report is displayed in the same order as the corresponding attributes defined above.

Cannibalization areas in the output can be further analyzed with Business Analyst tools and workflows to model change and identify the best course of action. For example, you can use the Enrich Layer tool to understand how many people live in the areas of overlap.