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General information

Overcrowding is defined here as having one or more persons per room.1 Overcrowding is connected with both physical illness, including communicable diseases, and mental stress.2

Key Findings

  • While 7% of San Mateo County households experience overcrowding, 13% of renters and 3% of homeowners experience overcrowding.
  • Daly City, Redwood City, west Menlo Park, and East Palo Alto had the highest percentages of overcrowded households, where more than 30% of households are overcrowded.


  • Data were obtained from U.S. Census Bureau’s 2009-2013 American Community Survey 5-year Estimates at American FactFinder.
  • Data were cleaned and aggregated to determine the percentage of overcrowding at the census tract level.
  • Data were mapped using ArcGIS for Desktop.
  • Data included all households.


  • Approximately 295,000 households are selected to participate in the annual American Community Survey, or less than 1 percent of all households in the U.S. 
  • Data were estimates based on survey responses, and not actual counts.  
  • Estimates have some chance of error.​


  1. U.S. Department of Housing and Urban Development, Measuring Overcrowding in Housing
  2. Robert Wood Johnson Foundation, Where We Live Matter for Our Health: The Links Between Housing and Health