Areas of Influence (AOI)
Another type of trade area is called an Area of Influence (AOI)/Equal Competition (also known as Thiessen polygons in honor of Alfred Thiessen, a meteorologist who pioneered the method of creating areas out of spatially distributed data). This type of trade area assumes that consumers will travel to the closest business district in their region based on “as-the-crow-flies” distances. The trade area is formed by lines drawn exactly halfway between each of the competing business districts. Any point within the equal competition area is closer to the subject business district than any of the surrounding business districts.
Since equal competition areas are based on as-the-crow-flies distances, these trade areas do not adjust for the way people actually travel on the ground. Further, they do not adjust for the drawing power of each competing business districts. Accordingly, it is helpful to use equal competition area maps along with drive time and other maps.