Seattle Transit Blog digs into the US Census data showing that multifamily units make up the majority of housing stock in Seattle, while the city's pool of single-family houses has shrunk over the past decade. What's more, that gap is bound to grow:
Just because a majority of the city is zoned for single family housing doesn’t mean that it makes up a majority of housing, which is makes sense when you think about what density actually means, more housing in less area.
The housing trends over the last ten years have seen growth in the medium/large multifamily housing (50+ units) and townhouses, which make up 4.5% and 1.4% more of the housing stock in 2010 than they did in 2000. This growth in their market share came overwhelmingly at the expense of single family housing representing 3.4% less of the housing stock in 2010 as it did in 2000. More importantly, this trend will never reverse, because Seattle essentially has no new buildable land for single family housing. As the city continues to grow, single family housing will continue to represent a smaller and smaller percentage of the city’s housing stock.
The whole post is full of good talking points for when various neighborhood groups squawk about the city shoving density in their pie holes and down their throats.