  A decision maker is choosing between an active action (e.g., purchase a
house, invest certain stock) and a passive action. The payoff of the active
action depends on the buyer's private type and also an unknown state of nature.
An information seller can design experiments to reveal information about the
realized state to the decision maker, and would like to maximize profit from
selling such information. We characterize, in closed-form, the revenue-optimal
information selling mechanism for the seller. After eliciting the buyer's type,
the optimal mechanism charges the buyer an upfront payment and then simply
reveals whether the realized state exceeds a certain threshold or not. The
optimal mechanism features both price discrimination and information
discrimination. The special buyer type who is a-priori indifferent between the
active and passive action benefits the most from participating in the
mechanism.
