[CTPP] ACS Data on Commuting

Greetings to CTPP-News: Well, this morning (August 29th) the Census Bureau released the socio-economic data tables from the 2005 American Community Survey (ACS2005). Some of the tables relevant to transportation planners & others are the journey-to-work related tables: workers by means of transportation; workers by travel time to work; and aggregate & average travel times. Users may also be interested in some of the limited "commute flow" data available: intra-place, intra-county, intra-MCD, commute-to-principal cities. The challenge is that the ACS2005 only includes data for persons-in-households, households, and workers-in-households. Comparable tables from Census 2000 aren't always that readily available. So, for HOUSEHOLD workers by means of transportation, we used CTPP Table 1-35, for Census 2000, to compare with the ACS. For HOUSEHOLD workers by travel time to work, we used Census 2000 PUMS; and for the average travel time by means of transportation for HOUSEHOLD workers, we also used Census 2000 PUMS. Comparable CTPP tables on household workers by travel time to work, or average travel time, are just not available. Data for our region (SF Bay Area) is included in the attached Excel workbook. The workbook contains: Table 1. Household Workers by Means of Transportation to Work by County of Residence, 2000 to 2005. Table 2. Household Workers by Travel Time to Work by County of Residence, 2000 to 2005. Table 3. Household Workers by Average Travel Time by Means of Transportation by County of Residence, 2000 to 2005. Table 1 is based on CTPP Table 1-35, Census 2000 PUMS (for bike/walk split for HH Workers), and ACS 2005, Table B08006. Table 2 is based on Census 2000 PUMS, and ACS 2005, Table B08012. Table 3 is based on Census 2000 PUMS, and ACS 2005, Table B08136. We are hard at work creating supplemental tables to report on the statistical significance of the differences. This is a chore as it requires calculating the standard errors for the Census 2000, and computing a z-statistic on the standard error of the difference between values. Z-statistics greater than 1.65 indicate a significant difference in the values or shares at the 90% confidence level; > 1.96 indicate a significant difference at the 95% confidence level, etc. What this does NOT do is calculate whether or not there is a "meaningful difference" between 2000 and 2005....That's more or less a professional judgment call. Data for Large Areas (65,000+ pop.) of WORK are expected for release on October 3rd (same release date for all of the household-related tables, including the household vehicle availability information.) PUMS. The ACS 2005 PUMS (Public Use Microdata Sample) was also released today, August 29th. Data is available in CSV and SAS format. The PUMS datasets appear complete (PUMA of Residence; POWPUMA - PUMA of Work appears to be the County of PUMA, whichever is larger, similar to Census 2000 PUMS....) The big headache with the ACS PUMS is that the Census Bureau has changed all of the variable names from a fairly mnemonic style to near gibberish: e.g., "JWTR" is the variable for "Means of transportation to Work", "COW" is for "Class of Worker" etc. Ah, well, we can adapt. It will be interesting to see the new stories emerging from this new set of ACS data. Stay tuned. cheers, Chuck Purvis, MTC ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) [new, 8/1/05] (510) 817-7848 (fax) [new, 8/1/05] www: http://www.mtc.ca.gov/ Census WWW: http://www.bayareacensus.ca.gov/ **************************************************************