Emmanuel Didier's project at the MPIWG was to turn his PhD dissertation (2001), into a book under contract with INED Press in France. The provisional title of the book was Comment les sondages ont exprimé l’Amérique. Une histoire des enquêtes partielles aux Etats-Unis pendant l’Entre-deux-guerre.
The purpose of the book was twofold. On the one hand, Emmanuel Didier was interested in the huge growth of statistical surveys realized by the US government during the interwar period. Didier looked particularly closely at those produced by the Department of Agriculture and by the Department of Labor. His aim was analyze how new methods—particularly random sampling—were developed during this period. On the other hand, his study showed how this new source of information about the nation was related to a new way of defining the nation (as there was a need for a new statistical definition of the US to make these surveys possible) and of governing the nation: the New Deal would not have become what is was without the new type of data, and Didier's booked served to explain why.
Finally, by showing how a new way of producing knowledge was linked to a new type of government, Didier characterized, by the means of the concept of expression, the precise link between knowledge and government, arguing that statistics and government have expressed a new America.