This message may be relevant to folks who use the CTPP data on households by the number of workers in the household (e.g., Table 1-65 households by workers in household by vehicles available). I've had a conversation with Phil Salopek (Census Bureau) about the definition of "households by workers in household" and I've confirmed this information by examining the 1% PUMS for my region. The CTPP Access Tool program defines "workers in household" as "see the definition for workers" and "see the definition for households" which is frankly not that useful. This could be improved. The CTPP documentation could be improved by providing a precise definition of "workers in household." It may not be what you think it is!!! The CTPP documentation is based on standard census documentation such as that from SF3. For example, the term "workers in families" is defined as the number of civilian employed with a job LAST YEAR (Question #30a on the census long form.) It is clear that the CTPP data on "workers in household" is based on "workers at work during census reference week" and is NOT BASED ON "workers at work, plus workers with a job but not at work" So, the values for "zero worker households" in the CTPP will include "households with no workers" PLUS it will include "households with worker(s), but the worker(s) are NOT at work LAST WEEK" The CTPP shows 539,755 "zero worker households" in the Bay Area, at 21.9 percent of total households. The 1-percent PUMS data shows 514,617 "zero worker households" in the Bay Area, at 20.9 percent of total households. 1-percent PUMS data, using the CTPP definition of workers in households, shows 538,741 zero-worker households. This means that we have 25,000 households that have workers, but all of the workers in the household were not at work "last week" (they were all having fun watching spring training baseball....) (For those using PUMS, the CTPP definition of workers in households is based on where ESR=1 or ESR=4, where ESR = employment status recode variable. The alternative definition of workers in households is based on where ESR=1, 2, 4, or 5, which includes the weekly absentees (ESR=2 and 5). I am assuming that the Census Bureau will not change the CTPP 2000 data since it is consistent with the 1990 CTPP data. My plan, for validation of our workers-in-household & vehicles-in-household model (WHHAO), is to depend on the 5-percent PUMS data to provide PUMA-level control totals, and to adjust the CTPP zone-level data (Part 1, Table 65) to match with the PUMS data. Hope this helps, Chuck Purvis, MTC ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 464-7731 (office) (510) 464-7848 (fax) www: http://www.mtc.ca.gov/ Census WWW: http://www.bayareacensus.ca.gov/ **************************************************************