Every time you step up to a photocopier, you can thank a man named Chester Carlson, born on this date in 1906. In 1938, he developed a method of making dry copies of documents on plain paper, known as xerography — which we take for granted in using photocopiers today. Before his invention, copies were made either by using carbon paper when typing or a mimeograph machine for large numbers of copies. Both were messy. The first commercial copiers became available in 1959. Now, making copiers is a $2.2 billion a year business in the U.S. You can find current data on the country’s economy by downloading the new “America’s Economy” mobile application at <www.census.gov/mobile>.