The term Midwest has been in common use for over 100 years. Another term sometimes applied to the same general region is "the heartland". Other designations for the region have fallen into disuse, such as the "Northwest" or "Old Northwest" (from "Northwest Territory") and "Mid-America". Since the book "Middletown" appeared in 1929, sociologists have often used Midwestern cities (and the Midwest generally) as "typical" of the entire nation. The region has a higher employment-to-population ratio (the percentage of employed people at least 16 years old) than the Northeast, the West, the South, or the Sun Belt states.