Valuations of Big Data can be extended to the generation of not only economic capital but also the other forms of capital elaborated by Bourdieu such as cultural and symbolic capital. Struggles over the production, dissemination and exchange of data involve struggles over the valuation of particular skills, education and expertise. How then does the classification of what constitutes the science and scientist of data mobilise specific resources, skills and investments? In this chapter we will approach this question by attending to a particular community of practice within which data science and its professionals are being talked about, conceived and implemented: national statistical institutes. Based on a multi-sited, multi-method and collaborative ethnography of the work of EU national statisticians, we draw on data from reports, discussions, interviews, meetings, and job descriptions to think about how a field and profession come into being in relation to but also as a critique of existing ones such as statistics and statisticians. What is understood to be lacking in the existing field and profession and what are the promises of the new are key questions that we pose to connect these issues to the politics of knowledge more generally.