While I haven’t waded into the zero-vehicle data as much as some
of you I would offer a few observations.
The share of zero vehicle households is somewhat misleading as it is
sometimes more or at least equally relevant to look at the share of the population
that lives in zero vehicle households. That number is about 60% of the
share of households and is surprising to folks when they realize the share of
population living in zero-vehicle households is quite small.
A few years ago there were some national polls about auto ownership/availability
for youth and there were some stunning numbers regarding how fast vehicle availability
was growing for youth. This is an interesting segment to explore
regarding vehicle saturation.
With high fuel costs we could have conflicting pressures where high
prices spur additional vehicle ownership in order to specialize vehicles, i.e.
keep that depreciated SUV for when you need it and buy that small car for
commuting. Marginal vehicle ownership costs in the
A couple years ago we did some analysis of the consumer expenditure
surveys with respect to vehicle availability and found that the highest
marginal spending per vehicle occurred in households that had more vehicles
than adults. We speculated that it is wealthier households in this
situation and that is where vehicle specialization begins. They add that
convertible or RV as an extra vehicle.
Steven E. Polzin, Ph.D.
Center for Urban Transportation Research
813-974-9849 (w)
813-416-7517 (c)
polzin@cutr.usf.edu
http://www.cutr.usf.edu
-----Original Message-----
From: ctpp-news-bounces@chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On
Behalf Of Chuck Purvis
Sent: Monday, July 28, 2008 11:45 AM
To: ctpp-news@chrispy.net
Subject: RE: [CTPP] ESRI article on ACS errors
Michael:
Short answer: very well.
Long answer:
The wording on the ACS vehicle availability question is identical to
the Census 2000 question. It's placement in the ACS is between the two
housing utility questions (plumbing/kitchen/telephone facilities, and
home heating), so these are all the "easy" housing questions
before one
has to answer the "difficult" housing questions (e.g., how
much is spent
on x, y, and z....)
We've done some county and regional level tabulations of our region's
auto ownership patterns, from 1960 to 2006, and the trends do make good
sense at both the regional and county level. There are some
ups-and-downs in the county-level zero vehicle shares, comparing 2000
to
2005 to 2006, but these may not be statistically significant. (We
published this data, released in I believe September 2007, for a
November 2007 regional workshop, url:
http://www.mtc.ca.gov/maps_and_data/datamart/census/)
Our regional share of zero-vehicle households has declined from 19.7%
in 1960, to 15.8% in 1970; 12.2% in 1980; 10.5% in 1990; 10.0% in 2000;
and then 9.5% in 2005, and 9.2% in 2006. This is for the nine-county
San
For
from 42.1% in 1960; 39.6% in 1970; 34.6% in 1980; 30.7% in 1990; 28.6%
in 2000; and then with the ACS: 31.3% in 2005, but dropping back to
28.6% in 2006 (same as 2000).
So, we're anxiously awaiting the 2007 annual ACS data that's scheduled
for released next month and September, and then the 3-year period
estimates (2005-2007) expected this December. The challenge will be how
to analyze and report all of this data in a timely manner, all the
while
trying to do our "regular jobs."....The other challenge: do
we just
report the estimates WITHOUT their standard errors necessary in
understanding the year-to-year, or period-to-period difference; or do
we
take the EXTRA time needed to report the estimates WITH the standard
errors (adding, or perhaps "delaying" the reporting of the
results by
say 3 to 6 months?
Chuck
**************************************************************
Charles L. Purvis, AICP
Principal Transportation Planner/Analyst
Metropolitan Transportation Commission
101
(510) 817-5755 (office)
(510) 817-7848 (fax)
cpurvis@mtc.ca.gov (e-mail)
www: http://www.mtc.ca.gov/
**************************************************************
>>> Michael.Cline@utsa.edu 07/28/08 7:38 AM >>>
Chuck (or others),
In your opinion, how well do you think ACS is estimating Zero Vehicle
Households? (or conversely household vehicle ownership?)
Michael E. Cline
Research Associate
Institute for Demographic & Socioeconomic Research
The
BB 4.06.10
(210)458-6537 f(210)458-6541
michael.cline@utsa.edu
http://idser.utsa.edu
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