Until the end of the 19th century, government statisticians were mainly concerned by censuses of population; demographic statistics attracted almost all of their interest. One could even say that demographic growth was considered then as the foremost indicator of a country's prosperity. In the beginning of the 20th century, however, most national statistical agencies experienced profound change: from then on, data relating to production and exchange would hold first rank; economists, being acknowledged specialists on these matters, would rapidly rise to the head of these agencies. This paper seeks to expose how such a transformation occurred in a specific case, that of Canada: it will do so by tracing the changing approaches to selected fields of inquiry, the emergence of new fields for data collection, and, above all, the rapid emergence, of some of the key concepts of classical political economy in duscussions among statisticians.