Many transactions are now computer mediated, making it possible for sellers to condition their pricing on the history of interactions with individual consumers. This paper investigates conditions under which price conditioning will or will not be used. Our simplest model involves rational...

I describe a simple two-stage mechanism, the compensation mechanism, that implements efficient allocations in economic environments involving externalities. The compensation mechanism can be used to solve a wide variety of externalities problems, including the standard problem of public goods...