I was not attempting to provide an academic analysis, because there are a lot of pitfalls and it takes someone who has the skills, experience, and time to fully parse all the data, and look for mistakes in methodology.  If only I had the time.  I did find this census data that is July to July, and not calendar yer, but it appears that metro growth in units exceeded growth in population, which illustrates how available data may be lacking:

http://www.oregonmetro.gov/news/portland-region-grows-235-million-residents-census-estimates-newcomers-leading-way

It is an indicator however that there may be more going on here that simply units and in migration to the region.

Yup, that is an interesting collection of data and analysis, though I don't know that it quite rises to the level of an academic study, needs peer review.

I would also be careful about using such data to apply to other regions, as there may be things like geography that SF has that other places like Portland do not.