This figure shows an economic topographical map of the United States' The altitudes are proportional

1
This figure shows an economic topographical map
of the United States. The altitudes are
proportional to gross product per area. The
observations measure economic activity in
millions of 1995 U.S. dollars per km2 at a 1º
latitude by 1º longitude scale. This is part of a
new data base (G-Econ 1.1) that estimates output
density for all terrestrial grid cells.