Much of the data pertaining to past economic performance available in today’s electronic databases differs from what was originally reported. What was initially reported was frequently incorrect or incomplete, and has since been revised and updated based on new information. In order to understand and create models of how economies and financial markets behave, however, economists often need to know what data was available to the public and to policy makers at a given point in time.

–Paraphrase of Katrina L Stierholz, Research Information Officer and Director of Library and Research Information, Federal Reserve Bank of St. Louis, presenting What Old News Tells Us That Data Does Not: The Uses of News Reports in Monetary Policy Research: via Center For Research Libraries