very time you fill a prescription at a drug store like Walgreens, the pharmacy keeps a record of the transaction, noting information such as your name, the drug, the dosage, and the issuing doctor. It’s a routine bit of bookkeeping, and for a long time it raised few eyebrows. Then a firm called IMS Health starting buying up the data. Mining pharmacy records, the company assembled profiles of hundreds of thousands of American doctors and millions of individual patients, with names and other identifying details encrypted. IMS Health turned around and sold access to those files to pharmaceutical companies, making it easier for the firms to target (and reward) the physicians most likely to prescribe expensive, brand-name drugs.