Cookies are extensively adopted in the current web scenario. A cookie is a small file placed on a user’s computer that permits a website to record information about a previous visit. From a strictly technical perspective, they contribute to a better user experience, for example, allowing a user to stay logged in on a website and a website to remember user preferences.

In practice, cookies have a significant impact on commercial markets as they can be (and are) used to target advertising. Recent trends clearly show websites, even competitors, sharing cookie information, generating the well-known concerns about user privacy.

This paper discuss information leakage in a commercial context where cookie matching could have, under the hypothesis of ideal conditions (in equilibrium), a fair impact on the market or could lead, in inhomogeneous conditions, to unbalanced perturbations. Indeed, in the latter case, information leakage determines imbalances that could help one (or few ones) and harm many ones (against the balanced model that produces the same benefit or damage for everyone).

I definitely enjoyed reading this paper for its clear premise, the strong approach, the rich model adopted for the analysis of the dynamics of interest across multiple scenarios, and the further directions previewed by the authors, including the analysis of other economic phenomena (such as market fragmentation).