  We derive robust predictions in games involving flexible information
acquisition, also known as rational inattention (Sims 2003). These predictions
remain accurate regardless of the specific methods players employ to gather
information. Compared to scenarios where information is predetermined, rational
inattention reduces welfare and introduces additional constraints on behavior.
We show these constraints generically do not bind; the two knowledge regimes
are behaviorally indistinguishable in most environments. Yet, we demonstrate
the welfare difference they generate is substantial: optimal policy depends on
whether one assumes information is given or acquired. We provide the necessary
tools for policy analysis in this context.
