The latest overall SF sales stats I have reflect the number of sales for Nov 07 (479 transactions) was down 15.7% from Nov 06 (479); and the median home price in San Francisco was up 7.5% over this same period.
In 94114 zip code 48.5% of the population has been in the same home 5+ years, and the zip skews a little older at a median age of 37.7 (2000 census), with unemployment 1.8% reported at that time. All this shows the stability of the neighborhood and In my experience people move to Noe and stay (I lived there 15 years myself).
I haven't calculated Noe sales for last year specifically, so I can't confirm that "they are at a historical low," which I doubt (I think 1990-91 may have been lower), although there were a number of TIC units that languished on the market due to lack of parking or awkward flow at the end of the year. Right now there is very little inventory in 2-4 unit buildings (not TIC units) across the City, and a lot of 1031 buyers looking.
In terms of relocations, people coming from metros such as New York, Boston or LA are more likely to buy than those who are coming from other areas who usually have such sticker shock they can't bring themselves to buy even if they qualify and intend to be here 5 years. NAR publishes a report showing migration patterns, although I haven't purchased it (it's $50 and may help you analyze part of your questions).
People who intend to be here a year or less won't be buying, but our corporate short term rental market is extremely healthy.
I'm not sure what insight you're looking to gain from the question, but I hope these few stats help. Let us know what you find out!