A mathematician is a device for turning coffee into theorems. -Paul Erdos
We have a natural tendency to oversimplify things because it’s easier to make sense of simple things than complex things. This map (at right) represents the simplest view of the relationship between a store and its customers. The two-mile radius around the store is a reasonable estimate of the trade area for the store, which means that most of the customers will be inside the circle. If this is true 90% of the time, we don’t care about the details of how customers make their choices. But what if only 70% of the customers are actually in the circle? 60%? 40%? At some point we have to consider a more complex set of factors that determine our true trade area and whether it contains enough potential customers to make a store successful.
Yesterday afternoon I got the urge to get some fresh air and a cup of coffee. I had some reading to do, so I wanted to go to a place where I could sit down and finish the coffee at the shop rather than bring it home. I’m omnivorous when it comes to coffee, meaning that I love any good cup of coffee whether it’s Dunkin’ Donuts, Starbucks or a local shop. I hate to waste gas and time, so the closer, the better. Considering all of this, I’m probably similar to nearly 50% of coffee drinkers in my area (although many people have a STRONG preference for Dunkin’, but that’s a New England thing that weakens as you move west in the U.S.).
Here is a map of my choices (See map below left). The closest place is a Dunkin’ (#4) that’s just like most Dunkins’ - comfortable and well lit, good coffee, but not a “cozy” place to read a book, especially since most of my friends go there and would like to chat. Starbucks has a store about seven miles to the north (#1) and another one three miles to the south (#6). Although I like the one that’s closer, I tend to see people I know and that could distract me from reading. However, the extra four miles is a big price to pay for anonymity. The other places are Heavenly Donuts (#3) and Aroma Café (#5). Heavenly is more like a Dunkin’, but I’m less likely to see someone I know. Aroma Café is more like a Starbucks, but I remember the price of coffee being high and the service was slow (the one time I went there). Besides, the Starbucks to the south (#6) is less than a mile farther down the road.
After deep thought, I decided to go to the Starbucks (#6) because I was willing to trade-off the risk of seeing someone I knew for all the other pros and cons of the other places (I knew I could pick a table in the back and face the wall if necessary).
What’s the point of this story? Many consumer decisions are too complex to model with simple assumptions about trade area definition, competitor effects, trip patterns and distance sensitivity. If I’m going to visit a client by car, I always go to the Dunkin’ closest to my house. If I want a breakfast sandwich served to me along with coffee, I go to Aroma Café. If I want to get away from the locals, I drive to the Dunkin’ or Starbucks in Andover, which is three times farther than the closest Dunkin’ and I’ll be driving past another Dunkin’ to get there.
Am I over thinking this? It’s true that often when we aggregate data in an area around a store (say a two-mile ring for coffee customers) the details of those customers’ decisions average out to give us an overall probability of capturing customers. But that isn’t always true. Dunkin’ #4 is on a main feeder to Interstate 93. Starbucks #1 is in the center of Andover with nice retail shops that draw affluent people who like to drink coffee in connection with shopping. There are three Dunkins’ along this 10-mile stretch (plus a few more in gas stations) and they all do well. If Starbucks put a third store near Dunkin’ #4, what would be the impact on the other two Starbucks? It certainly is more complicated than simply looking at the impact of Starbucks on Starbucks, because the other coffee shops are already capturing much of the potential Starbucks business near the existing stores.
Every chain store operator (retailer, restaurant, service business) must face the complexity of the retail marketplace and develop methods of estimating sales, cannibalization and competition effects that are as simple as possible, but no simpler (Einstein). At the end of the day, some good maps and demographic reports combined with local market info about competition and consumer preferences will give decision makers a better basis for real estate planning and site selection than a mathematical model that is partially blind to key factors in the real world.