PIP: The author describes the nominal registers of the Belgian population generated from the census, which are a valuable source of economic and demographic data for the nineteenth and twentieth centuries. More specifically, she outlines a project to put the data for the Liege area into machine-readable format, and discusses the procedures used to ensure maximum accuracy of the data included in the file. She also examines how coherence testing and automatic coding of professions and place-names are making the data more reliable for further use. (SUMMARY IN ENG)