We often see rivals locate very close to each other (e.g., CVS and Walgreens, Home Depot and Lowes, etc.). The question of how and when rivals choose to co-locate is interesting both in theory and in practice. Peter Klein explores the topic in class using a simple Hotelling model of spatial competition. Here, two firms with identical products choose where to locate on a street, assuming buyers: 1) are evenly distributed along the street, 2) prefer to shop at the closest store, and 3) will shop with the same frequency no matter what choice is made. The Nash equilibrium has the firms located next to each other in the middle of the street — if either locates to the left or right, it can attract more customers by moving toward the center, without losing those at the extremes.

That last assumption, that buyers will shop with the same frequency is central to the median voter theorem in a two party system. That is, people will vote with the same frequency regardless, so it is best for candidates to “co-locate in the middle” of the political spectrum.  Note however, that as this Politico piece suggests, voter turnout can be very much in question: “modern American elections are rarely shaped by voters changing their minds, but rather by shifts in who decides to vote in the first place.” Under these assumptions, having candidates at political extremes may be a winning strategy. In a similar fashion, firms must be aware of whether some customers will choose to stay out of the market if there is no seller located nearby.

Contributed by Peter Klein