This paper discusses alternative aggregations that can be used to code business sectors using the census information on different occupations and employment status categories of entrepreneurs and workers. The paper discusses how sector aggregations can be constructed that classify business proprietors by the type of economic activity in which they were engaged, and also the sector of activity for those that were clearly not entrepreneurs. It defines two classifications at two levels of aggregation that are used in subsequent analysis: ID18 and ID50 used for sector/entrepreneurship coding; and EA17 and EA51 used for sector/whole economically active coding. It compares this coding with the more detailed coding in I-CeM, that used for the PST occupational classification system devised by Wrigley, and with the codes used in modern mainstream industrial classifications of sectors and occupational groups.