section_path: Society/Economics
section_name: Economics
paragraph_text: Economics
  
  Historically, cities rely on rural areas for intensive farming to yield surplus crops, in exchange for which they provide money, political administration, manufactured goods, and culture. Urban economics tends to analyze larger agglomerations, stretching beyond city limits, in order to reach a more complete understanding of the local labor market.
  
  As hubs of trade, cities have long been home to retail commerce and consumption through the interface of shopping. In the 20th century, department stores using new techniques of advertising, public relations, decoration, and design, transformed urban shopping areas into fantasy worlds encouraging self-expression and escape through consumerism.
  
  In general, the density of cities expedites commerce and facilitates knowledge spillovers, helping people and firms exchange information and generate new ideas. A thicker labor market allows for better skill matching between firms and individuals. Population density enables also sharing of common infrastructure and production facilities; however, in very dense cities, increased crowding and waiting times may lead to some negative effects.
  
  Although manufacturing fueled the growth of cities, many now rely on a tertiary or service economy. The services in question range from tourism, hospitality, entertainment, and housekeeping to grey-collar work in law, financial consulting, and administration.
  
  According to a scientific model of cities by Professor Geoffrey West, with the doubling of a city's size, salaries per capita will generally increase by 15%.