Change in the Housing Stock

–The mix of single family and multi-family housing has remained almost contant for 30 years.

–King County has seen a shift toward multi-family while Pierce and Snohomish Counties have seen a shift toward single family.

–Since 2010 the region has added more multi-family housing than single family.

Preferences for housing types have changed very little

A key underlying assumption of regional growth strategies has been a shift in preference toward multi-family housing that could be built in urban centers, thereby lessening development pressures on the periphery.

This has not been happening. Figure 1 shows the change in the mix of housing in the three counties between 1990 and 2018. The single family share was constant from 1990 to 2010. Multi-family increased during that timeframe, but in just about the same proportion as mobile homes decreased. From 2010 to 2018 there was a 2 percent drop in the single family share in the region and a corresponding increase in multi-family share.

Different shifts in housing mix among three counties

The shift in the housing mix seen in Figure 1 plays out differently in the three counties. Figure 2 shows the change in each of the counties from 1990 to 2018, as well as the three-county change. Note that while King County saw a shift toward multi-family housing, both Pierce and Snohomish counties saw growth in the share of single family housing. In all cases, mobile homes saw a drop in share.

Shift since 2010

Figure 1 shows a small but noticeable shift between 2010 and 2018. This was due to two factors. First, is the massive build-up of multi-family housing in Seattle and East King County. Second are the ongoing challenges faced by the single family housing industry in the wake of the housing crash of 2008. The structure of the industry has changed and builders have difficulty getting financing.

Figure 3 shows the additions to the regional housing stock between 2010 and 2018. Note that while 60 percent of the existing housing stock is single family, only 42 percent of additions have been single family. It is unlikely that consumer preferences have shifted that quickly, so we can assume that there will be a shortage of single family housing available in the near to medium term.

Variation around King County

Within King County the housing mix varies widely. Figure 4 shows the housing mix by the public use microdata areas (PUMAs) of King County. The downtown Seattle PUMA, which includes the rapidly growing South Lake Union area, has by far the lowest share of single family homes. At the other extreme, the eastern part of the county has a fairly small share of multi-family. The remaining stock of mobile homes is mostly concentrated in South King County PUMAs.

Looking ahead

Housing preferences seem quite constant, and local governments have few policy tools to cause them to change. The shift away from single family in King County and the shift toward single family in Pierce and Snohomish counties has led to long commutes and people working in King County look for affordable neighborhoods to the north and south. The rapid growth of multi-family in Seattle and East King County has served the rapidly growing population of young singles.

Questions going forward are:

• Is the single family share of the housing stock—around 60 percent in the region—constant, or will it continue the decline seen since 2010?
• Will Pierce and Snohomish counties continue to provide affordable single family neighborhoods for middle income people working in King County?
• As millennials start families, will they find the single family homes that young families have historically preferred?