  A monopoly seller is privately and imperfectly informed about the buyer's
value of the product. The seller uses information to price discriminate the
buyer. A designer offers a mechanism that provides the seller with additional
information based on the seller's report about her type. We establish the
impossibility of screening for welfare purposes, i.e., the designer can attain
any implementable combination of buyer surplus and seller profit by providing
the same signal to all seller types. We use this result to characterize the set
of implementable welfare outcomes, study the seller's incentive to acquire
third-party data, and demonstrate the trade-off between buyer surplus and
efficiency.
