Demographic D.3 Per capita and household median income
Data Source
Applied Geographic Solutions, Inc. Spring 2007 Update: Current Year Estimates. Methodology available at: http://www.appliedgeographic.com/library.html.Map and table created by San Francisco Department of Public Health, Environmental Health Section using ArcGIS software.
Map data is presented at the level of the census tract, which was calculated by assigning census block data to census tracts based on spatial location. The map also includes planning neighborhood names, in the vicinity of their corresponding census tracts.
Table data is presented by planning neighborhood. While planning neighborhoods are larger geographic areas than census tracts, census tracts do not always lie completely within a planning neighborhood. SFDPH used ArcGIS software and a 'centroids within' methodology to convert census blocks to geographic mean center points. We then assigned census blocks 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.September_2009.pdf
http://www.thehdmt.org/data_map_methods.php
Explanation and Limitations
Per capita income is the mean income computed for every man, woman, and child in a geographic area. It is derived by dividing the total income of all people 15 years old and over in a geographic area by the total population in that area. Income is not collected for people under 15 years old even though those people are included in the denominator of per capita income.
In contrast to per capita income, weighted household median income presents an alternative picture of income distribution in San Francisco, accounting for the fact that many households pool their income. The neighborhood weighted median is calculated by weighting the respective census tract medians based on the number of households in each tract, and then applying the standard median calculation method.