This report series defines and measures the "information activity" within the national economy. "Information activity" is defined to include those specific industries and occupations whose primary function is to produce, process, or transmit economically valuable information. Changes in the national labor force are analyzed over a 120-year span. This volume presents reports of the 25 major industries that compose the primary information sector. Each report discusses the reasoning behind considering the industry as part of the primary information sector, a breakdown of the subordinate industries that compose the larger industrial category, a narrative of the informational aspects of the industry, and a report of the final demand and value-added components. The service, manufacturing, and construction sectors of the economy are considered. (Author/DAG)