The G-Econ research project is devoted to developing a geophysically based data set on economic activity for the world. The current data set (GEcon 4.0) is now publicly available and covers “gross cell product” for all regions for 1990, 1995, 2000, and 2005 and includes 27,500 terrestrial observations. The basic metric is the regional equivalent of gross domestic product. Gross cell product (GCP) is measured at a 1-degree longitude by 1-degree latitude resolution at a global scale. Updates will be posted as they become available. The project staff is Professor William Nordhaus, Yale University, and Professor Xi Chen, Quinnipiac University. Email contacts are william.nordhaus@yale.edu and xi.chen@quinnipiac.edu. (Last revision, May 2011)