Data brokerage firms are also companies that collect data but more with an intention of “packaging” and selling any personal information related to financial, demographic, criminal, political, recreational, and social activities as well as data about general interests, purchase behavior, and the health of individuals. … There is even the practice of onboarding, which involves matching data from one’s offline activity (gathered, for example, if you give your email address in the middle of a transaction that you thought was offline) with the much larger amount of data available about one’s online activities.

Nick Couldry & Ulises A. Mejias, The Costs of Connection, loc. 202