QA Environment
Progress Indicators
Housing diversity
Basics
Puget Sound Indicator Name
Housing diversity
Progress Indicator
Each Unit (count)
/
Topics
Smart Growth
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Contributing Partners
Last Updated
01/09/2025 00:35:21
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HD_ex15_mu-percent-map-allPS (1).png
Multi-unit housing as a percent of total housing units permitted in the Puget Sound region between 2017 through 2023.
Related Ongoing Programs
Description

Percentage of total new housing production that is multi-unit (e.g., apartment buildings, condominiums, townhomes, etc.).


A high value for this indicator suggests that the jurisdiction is successfully adding diversity to the housing supply by providing a greater variety of unit types and sizes to meet a greater variety of household needs.

Progress Indicator Chart

Promoting smart growth in the Puget Sound region is a key strategy for the recovery of the Puget Sound ecosystem. The production of multi-unit housing is an essential part of this strategy. Multi-unit housing types require less land area for each new unit than single-unit options; these types can thus accommodate more growth through compact development[1]. In the process, multi-unit housing can help conserve forest lands, open spaces, agricultural lands, and other natural ecosystems in Puget Sound.

Multi-unit housing production also supports housing affordability. Recent changes to the GMA require jurisdictions to plan for and accommodate housing affordable to all income levels[2]. Compared to detached housing, multi-unit housing like apartments can be much less costly to produce per unit[3]. Enabling and encouraging the production of multi-unit housing is one way that jurisdictions can offer housing options to all income levels[4].

This indicator is one way to assess progress across jurisdictions in offering more diverse housing options. It is calculated at the jurisdiction scale because jurisdictions (cities, towns, and counties) have control over zoning and development regulations that dictate the types of housing built. This indicator, measured at the jurisdiction level, can help local planners evaluate how their policies support improved housing diversity.  


[1] Puget Sound Regional Council (2020). Multifamily Development, Housing Innovations Program, Puget Sound Regional Council, Washington. https://www.psrc.org/media/2049.

[2] Washington State Department of Commerce (2024). Growth Management Act Amendments 1995-2024. Washington State Department of Commerce, Washington State. https://deptofcommerce.app.box.com/s/41vk2hbhsder8movy8kmlylbwac6v7ik.

[3] Puget Sound Regional Council (2018). “Missing Middle” Housing in the Region, Puget Sound Regional Council, Seattle, Washington. https://www.psrc.org/media/4938.

[4] Puget Sound Regional Council (2020). Housing Options in Expensive Markets, Housing Innovations Program, Puget Sound Regional Council, Washington. https://www.psrc.org/media/3212.

Key Progress Indicator Results

The region is getting better at increasing the percentage of total housing production that is multi-unit. In the current reporting period (2017-2023), an average of 66 percent of new housing was multi-unit each year compared to an average of 53.7 percent each year during the baseline reporting period (2010-2016). 

  • Since 2010, multi-unit housing increased dramatically as a percentage of all units produced, from a low of 43 percent in 2011 to a high of 73 percent in 2023. 
  • This trend represents considerable progress over time, though the number of new housing permits is also increasing over time. The progress in this indicator may then be attributed an increase in the number of multi-unit housing permits rather than a decrease in single-unit housing permits.
Methods
Monitoring Program

Office of Financial Management, State of Washington.

Data Source

Annual housing permits from 2010 through 2023, Washington Office of Financial Management.

This Progress Indicator relies on data published by the Washington State Office of Financial Management (OFM). OFM publishes annual data on housing units permitted, by housing type. This indicator is calculated by dividing the number of multi-family housing units permitted by the total housing units permitted.

This indicator is calculated over a six-year period. In smaller cities and counties, a single large project can significantly impact the value of this indicator. The six-year calculation period helps minimize noise in this indicator and matches reasonably well with comprehensive planning cycles. Comprehensive plans directly influence how Washington counties address population growth.

Current reporting period: 2017 through 2023

Baseline period: 2010 through 2017

 

We evaluate progress by comparing the region performance in the current reporting period to performance during the baseline period.

 

Limitations

This Progress Indicator helps assess progress offering diverse housing options across Puget Sound. Diverse options can better support community needs and population growth. But this indicator has limitations:

It presents a simplified view of housing production trends.

  • This indicator does not differentiate between different multi-unit housing types. We cannot say how much of the multi-unit housing production is in the form of large apartment buildings, for example.
  • OFM does publish data on the types of multi-unit housing permitted and PSP can explore these data in more detail in the future.

It ignores the location of new housing in relation to important natural resource lands.

  • This indicator does not evaluate whether housing is being built within Critical Areas and Natural Resource Lands, like farmlands.
  • This indicator should be evaluated alongside Farmland Conversion and Forestland Conversion indicators (in development), and Habitat Function indicators to get a more complete picture of land cover change inside and outside of urban areas.

 

View a detailed report of the methods used to calculate this Progress Indicator here.

Critical Definitions

Urban Growth Area (UGA): Areas designated by counties within which urban growth shall be encouraged and outside of which growth can occur only if it is not urban in nature (RCW 36.70A.110). 

Interpretation of Results

This indicator illustrates that the region is improving the percentage of new housing that is multi-unit in the current reporting period (2017-2023) relative to the baseline period (2010-2016). In the current reporting period, an average of 66 percent of new housing was multi-unit each year compared to an average of 53.7 percent each year during the baseline period. We thus apply the “Getting Better” designation, though note that individual jurisdictions vary in their progress developing more multi-unit housing options across Puget Sound.

 

Baseline period (2010 through 2016): 53.7 percent of new housing is multi-unit each year, on average.

Current reporting period (2017 through 2023): 66 percent of new housing is multi-unit each year, on average.

 

Nearly all counties improved performance over time, but progress at the jurisdictional level varied across Puget Sound. 

Market conditions vary across counties, likely affecting progress in this indicator.

  • Between 2017 and 2023, King county had the highest percentage of multi-unit production at 83 percent while Mason county had the lowest percentage of multi-unit production at 1 percent.
  • This wide range in performance reflects different housing market conditions across highly urban and smaller rural counties.

Nearly all counties saw improvement over time. 

  • All counties, except for Mason, improved their performance in this indicator in 2017 through 2023 compared to 2010 through 2016. Mason county’s performance decreased by 3 percent between these two periods.
  • Skagit (+30 percent), Kitsap (+21 percent), and Thurston (+17 percent) counties saw the greatest improvement in the percentage of new housing that was multi-unit between these two periods.

Performance varies considerably by jurisdiction. 

  • King county had the greatest total amount of multi-family housing permits (131,179 permits between 2017 through 2023) of all counties. This is likely attributed to high demand for dense living in Seattle.
  • Many additional cities are transit-oriented development near current or forthcoming Sound Transit Link light rail or bus rapid transit service. This transit-oriented development represents a shift away from single-family housing. Cities include Redmond (94 percent multi-unit housing, 2017-2023), Shoreline (94 percent multi-unit housing, 2017-2023), Olympia (77 percent multi-unit housing, 2017-2023), and Bellingham (80 percent multi-unit housing, 2017-2023), among others.
  • Unincorporated UGAs typically scored much lower in this indicator between 2017 through 2023; unincorporated UGAs also contain a large share of new housing production. However, unincorporated UGAs in Clallam, King, Kitsap, Pierce, Snohomish, San Juan, and Thurston did improve in this reporting period relative to the baseline period.
  • Rural areas typically scored the lowest. This is expected due to county zoning and development regulations that tend to discourage or prevent multi-unit housing production in rural areas.

       View results by jurisdiction in the full indicator report.

This indicator has improved over time across the region; this suggests that housing production policy landscapes are increasingly supportive of housing diversity and smart growth. However, progress varies by jurisdiction. This variation is likely linked to two key factors, described below. Additional research into local circumstances is necessary to diagnose specific problems and effective strategies.

 

Local zoning, development regulations, and incentives:

Changes in local housing market conditions: 

  • Market conditions can also change housing production trends. Improvements to water and sewer infrastructure, new amenities, new transportation, etc. can modify the market and influence housing production demand and trends.
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Subcategories

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