We classify the sources of data into two broad categories: primary
Secondary data is data that somebody else has collected and made available for others to use. The U.S. government loves to collect and publish all sorts of interesting data, just in case anyone should need it. The Department of Commerce handles census data, and the Department of Labor collects mountains of, you guessed it, labor statistics. The Department of the Interior provides all sorts of data about U.S. resources. For instance, did you know there are 250 species of squirrels in this country? If you don’t believe me, go to www.npwrc.usgs.gov/resource/distr/mammals/mammals/_squirrel.htm
and you can become ...