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 contains the executive summary and the major findings of the study. It defines information and includes a formal set of National Income and Product Accounts for the primary and secondary information sectors, with input-output matrices for both of these sectors. In addition, it specifies the information-related occupations of both the primary and secondary information sectors. Finally, it presents lists of information policy issues pertaining to industry, government, and the home and makes two recommendations as to how the Federal government might meet the public policy issues posed by the expansion of our information activity. (Author/DAG)