My particular email system (WordPerfect Office, late Neocene age
network software) doesn't permit me to snip and edit Michael
Perelman's response, but I'll try to take each of his questions
one by one.

Michael asks "do demographics figure into the changes?"  Yes,
they do.  Among other things, average and median household sizes
in the urban areas have been declining over the last several
decennial censuses.  The more households you have, the more
housing you need.  The source of these changes in household sizes
are complex, but include factors like:  the divorce rate, overall
population boom (and boomlet/echoes of boomers' kids having
kids).  It's generally too, at least from my review of California
demographic data that rural counties have large households on the
whole than the urban counties.

The increasing conversion of apartments into condos I'm not so
familiar with.  I do think that, as in my earlier post, there is
a demand among lower-income people and small households for home
ownership - again, to control some part of this earth, to call
their own - that developers are starting to recognize.  So, for
example, right now there is a live/work development in West
Berkeley that just recently converted to condominium ownership
structure.  Three units in this development were designated
"inclusionary," and one is up for a lottery this Friday to
determine who gets to buy a unit priced at $96,200.  This unit
was advertised in the Sunday SF Examiner Real Estate section and
the marketing agent and I have been besieged with interested
applicants.  If you can provide ownership opportunities at such a
low price, people will jump at the chance.

At bottom, though I've not studied it systematically, my
experience as a housing planner indicates that many people at all
income levels would much prefer, given the opportunity, to pay
into their own equity, not someone else's, as well as for the
opportunity to control their home environment.

Insofar as data are collected on homeownership, I believe the
1990 census might be the first census to include data on condo
ownership as distinct from single-family or duplex ownership.

My colleague Jeff Levin of the City of Oakland may be out there,
having posted to this list recently.  He may have some comments
as well.