This Planet Money episode explains this well, and walks through a day in the life with one of the people who actually walks around and monitors prices. http://

This Planet Money episode explains this well, and walks through a day in the life with one of the people who actually walks around and monitors prices. http://www.npr.org/sections/money/2010/10/22/130757997/the-friday-podcast-the-price-of-lettuce-in-brooklyn http://www.npr.org/sections/money/2010/10/22/130757997/the-f...