Wal-Mart has an incentive to keep its stores close to each other so it
can economize on shipping. For example, to make this simple, just think
about a delivery truck: If Wal-Mart stores are relatively close
together, one truck can make numerous shipments; however, if the stores
are spread out, you wouldn’t have that benefit. So, I think that the
main thing Wal-Mart is getting by having a dense network of stores is
to facilitate the logistics of deliveries.
There are other benefits, too. Opening new stores near existing stores
makes it easier to transfer experienced managers and other personnel to
the new stores. The company routinely emphasizes the importance of
instilling in its workers the “Wal-Mart culture.” It would be hard to
do this from scratch, opening up a new store 500 miles from any
…Wal-Mart waited to get to the plum locations until it could build out
its store network to reach them. It never gave up on density.
The placement of Wal-Mart stores has followed a spatial diffusion model. K-Mart, in contrast, scattered its stores across the country. Here is more. Here is a video showing the spread of Wal-Mart, well worth watching and short. It is the best single lesson in economic geography you will receive. Thanks to http://kottke.org for the pointer.