Even though over 56 percent of U.S. households own a HD television set, less than 20 percent of television is actually viewed in true high definition. How is it that 80 all T.V. viewing is still in standard definition? In many homes people have both standard and high def sets, so viewing gets split. Also, on most HD sets 20 percent of the viewing is through non-HD feeds. Read the full story on nielsen.com