The Thurston region has made substantial investments in the infrastructure in urban corridors and centers, which are located in the Lacey-Olympia-Tumwater urban area. These areas serve as the region's primary economic hubs, capturing around 13% of the total assessed land value even though they contain just 1% of the county's land area.
Between 2012 and 2019 there was a 2% decrease in the share of assessed value in centers and corridors. At the same time, investment in north county urban areas outside a corridor, center, or infill area, increased 3%.
The average density of new residential development in urban centers and corridors has declined since the late 1990s, but housing density in urban infill areas and other urban areas (in all jurisdictions) has increased during the same period of time.
Residential density impacts the viability of transit service. In general, seven dwelling units per acre is the minimum density needed for transit service, and 15 units per acre (along with a mix of jobs and activities) is needed to support frequent transit service (service every 15 minutes or less).