Healthy Development Measurement Toolkit

Indicator HH.1.d Proportion of households living in overcrowded conditions

Data Source

Map and overcroding table data from: U.S. Census 2000, Geolytics software. Census variables used: 'Owner-occupied housing units with 1.01 to 1.50 occupants per room' (OWNCR100); 'Owner-occupied housing units with 1.51 to 2.00 occupants per room' (OWNCR150); 'Owner-occupied housing units with more than 2.00 occupants per room' (OWNCR200); 'Renter-occupied housing units with 1.01 to 1.50 occupants per room' (RNTCR100);'Renter-occupied housing units with 1.51 to 2.00 occupants per room' (RNTCR150); 'Renter-occupied housing units with more than 2.00 occupants per room' (RNTCR200); 'Total households' (NUMHHS0).

Map and overcrowding table created by San Francisco Department of Public Health, Environmental Health Section using ArcGIS software.

Number of bedrooms table created by SFDPH using data from:  SF Planning Department. 2005 Housing Inventory and Draft April 2009 Housing Element.  Available at: http://www.sfgov.org/site/uploadedfiles/planning/Citywide/pdf/Housing_Inventory_2005_web.PDF and http://housingelement2009.sfplanning.org/.

Map data is presented at the level of the census tract. The map also includes planning neighborhood names, in the vicinity of their corresponding census tracts.

Table data is presented by planning neighborhood. Planning neighborhoods are larger geographic areas then census tracts. SF DPH used ArcGIS software and a 'centroids within' methodology to convert census tracts to geographic mean center points. We then assigned census tracts to planning neighborhoods based on the spatial location of those geographic mean center points and calculated the planning neighborhood totals for the table.

Detailed information regarding census data, geographic units of analysis, their definitions, and their boundaries can be found in the HDMT at the following links:

http://www.thehdmt.org/etc/Geographic_Units_of_Analysis.pdf

http://www.thehdmt.org/data_map_methods.php

Explanation and Limitations

The U.S. Census collects data on overcrowding in housing units. The most common measure of overcrowding is persons-per-room in a dwelling unit. Other popular definitions of overcrowding include: the total number of persons in a unit, regardless of unit size; the ratio of persons to floor space in square feet; and the person-to-size ratio adjusted for household composition, structure type, location, or lot size.

For this indicator, overcrowding, as defined by the U.S. Department of Housing and Urban Development (HUD), is greater than 1.01 people per habitable room. Severe overcrowding is defined as greater than 1.51 people per habitable room.

A September 2007 report titled "Measuring Overcrowding in Housing" prepared for HUD, discusses different methodologies to measuring overcrowding and also briefly discusses the history of overcrowding. For example, the report states that "Over time, the prevalence of overcrowding has decreased. This finding is not surprising. As people's standard of living improved and additional debt-financing instruments became available, more people could afford to buy homes and/or upgrade to larger ones. Further, as home ownership rates increased (and non-ownership rates declined), the average house size increased. Simultaneously, we have seen a decrease in household size over the past 20 years. As a result of all these factors, people now tend to be less crowded in their homes than in years past."

The report continues to note however, that "Within urban areas, the rate of overcrowding is the highest in central cities. Relative to other urban areas, central cities tend to have a higher concentration of renters, lower income households, and foreign-born population which are more likely to live in overcrowded homes." Importantly, the report also states that "in relative terms (i.e., percentage terms) overcrowding in all four ethnicity/race categories declined for both measures over the past 20 years to 2005."

For more information, visit: http://www.huduser.org/publications/polleg/overcrowding_hsg.html

Why is this a Community Health Indicator?

The impacts of overcrowding on health are both direct and indirect. Most immediately, crowding increases risks for respiratory infections such as tuberculosis and ear infection.^a Overcrowded housing has also been associated with increased mortality rates (particularly for women), meningitis, and Helicobacter pylori bacteria which can cause stomach ailments.^b Crowded housing conditions also contribute to poor child development and school performance, in part, because overcrowding limits the space and quiet necessary for children to do homework.^c,d Overcrowding may act cumulatively with other environmental health stressors. For example, one recent study found that crowding combined with noise significantly increases chronic stress hormones in low-income children.^e Finally, overcrowding affects health indirectly by creating conditions conducive to poor sanitation, high environmental noise, and residential fires.