It doesn't depend on the size of the area. (I wish it did!)

In my area (a few miles from my house - population less than 10,000), a couple of years ago there were 3 locations in the same strip mall! I'm not sure how many there are in the near 20 mile area, but I do know there are more than in the entire Seattle area!

Now, about 35 miles away, there are 4 locations on the same street! (3 of them are in the same parking lot, the other 1 is all the way across the street!) And that area is only 5,000 to 10,000 also!