Housing & Transportation >> Notes & Sources

Housing: Notes & Sources


Affordability is measured by the percent of income spent on housing, the availability and cost of housing units, and the gap between what housing costs and what families can pay. According to the U.S. Department of Housing and Urban Development, 30% of gross income is the most that all but wealthy households can pay for housing without creating an excessive cost burden. Housing that costs more than 30% of income is considered “unaffordable.” 

Affordability gap forhome ownershipisthe difference between the median house (or condo) sales price and the average price that a median-income family can afford to pay.  Calculation of the affordability gap assumes that a “reasonable” monthly payment is no more than 30% of income for renters and home buyers. The “reasonable” or “affordable” monthly payment for homeowners includes estimated heating and utility bills and taxes, which, with the housing payment, are assumed to approximate 30% of household income for all but the highest-income households.  

Affordable home price, based on conventional lending assumptions with a 10% down payment, is one for which monthly payments on a 30-year mortgage loan at prevailing market interest rates take up no more than 25% of household income. Selected owner costs (utilities, heating and taxes) are assumed to contribute an additional 5% to the monthly payment.

Affordable rental units. Household income levels for affordability analyses are defined by the U.S. Department of Housing and Urban Development (HUD) as a percentage of the median household income in the local area. This local median income standard adjusts for regional differences in costs of living and housing. In the following descriptions, American Community Survey 2010 median household income for King County ($66,174) is used.  In 2010, a median-income renter made 62.5% of the local median income, or about $41,400; a moderate-income renter made 50% of local median, or about $33,100; and a very-low-income renter made less than 30% of the local median (less than $19,900).

Confidence Interval (also known as error bar) is the range of values that includes the true value 95% of the time. If the confidence intervals of two groups do not overlap, the difference between groups is considered statistically significant (meaning that chance or random variation is unlikely to explain the difference).   

Foreclosure is a process that allows a lender to recover the amount owed on a defaulted loan by selling or repossessing the property that secures the loan.

  • The foreclosure process begins when a borrower/owner defaults on loan payments (usually mortgage payments) and the lender files a public default notice, called a Notice of Default. A Notice of Trustee Sale (NTS) is filed at least 30 days after the notice of default.
  • There is no single point in the process that experts call “a foreclosure.” Unlike Notices of Default, Notices of Trustee Sale must be recorded with the King County Recorder’s Office. Not all NTS filings result in loss of the dwelling. A settlement may be negotiated, or a borrower may pay what is owed, removing the NTS. Since King County does not require documentation of the removal of an NTS or the sale of a foreclosed house, the NTS serves as a proxy for serious delinquency in housing finance.

Homelessness is a term that refers to being without permanent housing. People who are homeless may live on the streets; stay in a shelter, mission, single-room occupancy facility, or abandaoned building or vehicle; or in any other unstable or non-permanent situation. People who "double up" (stay with a series of friends and/or extended family because they are unable to maintain their own housing situation) are also considered to be homeless.

Market rents of houses and apartments in small buildings (fewer than 20 units) are generally higher than rents in large buildings, so affordability is typically estimated using data on rents in buildings of 20 or more units.

Median home sale price is the middle of the range of home sale prices; half of all home sales were less and half were more than the median price.

Median income is the income earned by the middle household if all households are arranged in order according to income. (The American Community Survey 2010 median income for King County was $66,174.)

Race/Ethnicity: Federal standards mandate that race and ethnicity (Hispanic origin) are distinct concepts requiring 2 separate questions when collecting data from an individual. "Hispanic origin" is meant to capture the heritage, nationality group, lineage, or country of birth of an individual (or his/her parents) before arriving in the United States. Persons of Hispanic ethnicity can be of any race. Communities Count's terms for racial/ethnic groups are derived from those used by the U.S Census Bureau in 2010.

  • Communities Count terms:  Hispanic, Non-Hispanic, White Non-Hispanic, Black, American Indian/Alaska Native (AIAN), Asian, Native Hawaiian/Pacific Islander (NHPI), White, and Multiple Race (Multiple). Persons of Hispanic ethnicity can be of any race and are included in other racial categories. Racial/ethnic groups are sometimes combined when sample sizes are too small for valid statistical comparisons of more discrete groups. 
  • 2010 Census terms: Hispanic or Latino, Not Hispanic or Latino, White alone (Not Hispanic or Latino),  Black or African American, American Indian or Alaska Native, Asian, Native Hawaiian or Other Pacific Islander, White, Some Other Race, and Two or More Races.

Subsidized rental units. The approximately 65,250 King County rental units receiving some form of public subsidy represent about 20% of the County’s 322,500 occupied rental units.

  • About one quarter of subsidized units are priced to be affordable for very low-income households (less than 30% of local median income, or $19,900).
  • Another 37% are affordable for moderate-income households (those earning between 30% and 50% of local median income, or $19,900 to $33,100).
  • 22% target households earning between $33,101 and $53,000.
  • The remaining subsidized units support households with incomes up to $66,174, the local median income.
  • Most subsidized rental units are not set aside for households within particular income limits, so a subsidized unit that’s affordable for a household earning <$19,900 may be occupied by a higher-income household.


Data Sources

Data on percent of households that paid 30% or more of income for housing in King County, 1989-2014, come from the 1990 US Census (Table H058 ) and 2000 U.S. Census (Table H94 for 1989 and 1999, respectively), and the 2014 American Community Survey (Table B25070 for renters and Table B25101 for owners by mortgage status).  http://factfinder2.census.gov/main.html

Data on percent of King County renters and owners who paid more than 30% of income for housing by income range are from the 2013 American Community Survey, Tables B25101 and B25074. http://factfinder2.census.gov/main.html

  • For renters, housing costs include monthly rent, utilities and fuels.
  • For owners, housing costs include mortgage payments, real estate taxes, insurance, utilities, and fuels. They also include monthly condominium and mobile home costs.

Data on percentages and numbers of affordable rentals by income and city comes from Table B25063 of the2006-2010 American Community Survey, as computed in the Technical Appendix B for Housing, 2012 King County Comprehensive Plan (updated November 4, 2013) (http://www.kingcounty.gov/property/permits/codes/growth/CompPlan/2012Adopted.aspx

Data on supply and demand for affordable rental units by household income in King County, 2010, come from Table QT-H2, 2010 U.S. Census, and TablesB25063 and B25118, 2010 American Community Survey (http://factfinder2.census.gov/main.html ).  Data on the supply of subsidized rental units come from the Technical Appendix B for Housing, 2012 King County Comprehensive Plan (updated November 4, 2013) (http://www.kingcounty.gov/property/permits/codes/growth/CompPlan/2012Adopted.aspx

Data on the housing affordability gap come from the Technical Appendix B for Housing, 2012 King County Comprehensive Plan (updated November 4, 2013) (http://www.kingcounty.gov/property/permits/codes/growth/CompPlan/2012Adopted.aspx) Annual median home sale prices were obtained from the King County Assessor database of all sales in 2010. Single-family home prices include townhouses and condominiums, except where noted.  2010 income estimates are from Table B19013 of the 2010 American Community Survey. (http://factfinder2.census.gov/main.html )

Data on the 2010 distribution of housing in King County (renter occupied, owned with mortgage, and owned free-and-clear) came from Table QT-H2, U.S. Census 2010, (http://factfinder2.census.gov/main.html)

Data on the income distribution of owners and renters in King County, 2013, came from Tables S2506, S2507 and B25118, 2013 American Community Survey 1-year estimates (http://factfinder2.census.gov/main.html ).

Data on foreclosures came from the website of the King County Recorder (

The database was queried monthly by “Notice of Trustee Sale,” and the total number was recorded.  This count includes duplicate filings at a single point in time, and repeat filings on a property if a Notice of Trustee Sale is filed later in response to a subsequent delinquency. However, the percentage of duplications has not changed since 2006, so the Recorder number filed remains a reasonable indicator of overall foreclosure activity.  Estimates of numbers of housing units by year for 2001-2009 come from Puget Sound Regional Council (http://www.psrc.org/data/pophousing/pophousing-estimates). Count of total housing units and housing units owned with a mortgage in 2010 comes from Table QT-H2, 2010, U.S. Census.  Estimates of percentage of housing units with mortgages come from Tables B25003 and B25081, American Community Survey 2005-2009 by year (http://factfinder2.census.gov/main.html).

Data Table for Numbers and Percentages of Affordable Housing by King County City (2009-2013)

City By Region# Rental Housing UnitsAffordable to Households with ½ Median Renter IncomeAffordable to Households with Median Renter Income

North Region

  Number Percent Number Percent
Shoreline 7,601 777 10.2%  3,837 50.5%
Bothell (King County part) 4,612 176  3.8%  1,667 36.1%
Kenmore 2,037 36 1.8% 839 41.2%
Woodinville 1,795 106 5.9% 765 42.6%
Lake Forest Park 902 15 1.7% 343 38.0%


153,515 14,779 9.6% 79,049 51.5%
South Region          
Kent 18,674 1,399 7.5% 11,465 61.4%
Renton 16,907 1,291 7.6% 8,156 48.2%
Federal Way 15,145 660 4.4% 8,779 58.0%
Auburn 11,020 764 6.9% 7,075 64.2%
Burien 8,275 789 9.5% 5,416 65.5%
SeaTac 4,779 160 3.3% 3,180 66.5%
Tukwila 4,399 292 6.6% 3,025 68.8%
Des Moines 4,335 255 5.9% 2,420 55.8%
Enumclaw 1,619 217 13.4% 1,142 70.5%
Maple Valley 1,483 32 2.2% 426 28.7%
Milton 1,197 33 2.8% 657 54.8%
East Region          
Bellevue 22,656 859 3.8% 6,058 26.7%
Redmond 11,442 326 2.8% 2,743 24.0%
Kirkland* 11,380 341 3.0% 3,256 28.6%
Issaquah 5,052 320 6.3% 1,191 23.6%
Mercer Island 2,547 81 3.2% 515 20.2%
Sammamish 1,784 42 2.4% 219 12.2%
Newcastle 1,056 26 2.5% 334 31.6%
North Bend 848 95 11.2% 397 46.8%
Snoqualmie 794 41 5.2% 140 17.6%
Duvall 402 0 0.0% 52 12.8%

*Greater Kirkland includes CDP areas annexed since the last Census: Juanita Kingsgate and Inglewood Finn Hill. 

Data Sources: 2009-2013 American Community Survey


Other Sources

Background on the relationship between foreclosure and health can be found at:

  • Craig E. Pollack and Julia Lynch. Health Status of People Undergoing Foreclosure in the Philadelphia Region. American Journal of Public Health: October 2009, Vol. 99, No. 10, pp. 1833-1839.
  • Dawn E. Alley, Jennifer Lloyd, José A. Pagán, Craig E. Pollack, Michelle Shardell, and Carolyn Cannuscio. MortgageDelinquency and Changes in Access to Health Resources and Depressive Symptoms in a Nationally Representative Cohort of Americans Older than 50 Years. American Journal of Public Health: December 2011, Vol. 101, No. 12, pp. 2293-2298.

Definition of homelessness came from the National Health Care for the Homeless Council at http://www.nhchc.org/faq/official-definition-homelessness/.  

Background on student homelessness came from Columbia Legal Services brief at http://columbialegal.org/student-homelessness-WA and "Academic Achievement Trajectories of homeless and highly mobile students: Resilience in the context of chronic and acute risk" in Child Development. 2013 May-Jun; 84(3): 841-57. doi: 10.1111/cdev.12013. Epub 2012 Oct 30, at http://ftp.serve.org/nche/downloads/acad-ach-res-article-oct2012.pdf

Rates of student homelessness in King County school districts were calculated using data from the following sources:

Maps of King County covering a wide range of topics can be accessed at http://www.kingcounty.gov/operations/GIS/Maps.aspx#PH.  Maps most immediately relevant to Communities Count are under the headings of Community data & demographics, Public health, and Environment & natural resources, but other maps should be useful as well (farmers markets, transit routes, walking and biking routes, parks, traffic counts, etc.).

Quotes:  Communities Count interviewed 32 King County parents or guardians raising at least one child younger than 6 years of age.  We reached out to communities of color, recent immigrants, and residents with limited English proficiency to achieve a broad range of racial, cultural, and socioeconomic diversity. We interviewed both families with very low household income and those who earned up to median income (about $68,000 for a family of four in 2010). Family structures included single-parent households, couples living in consensual unions, married couples, and extended families.  Communities Count also interviewed service providers from several organizations in King County.