Re: [CTPP] income sources

Kendra: The two Census 2000 datasets, SF3 and CTPP Part 1, are derived from the same set of Census 2000 long form raw data, so they really should show the same patterns (households by household income) at the region, county, tract, block group and TAZ level. The SF3 (Summary File #3) definitely does NOT have TAZ-level tabulations, but it sounds like you have a process to use census block groups to aggregate/disaggregate into your TAZ structure. The SF3 table P-52 provides data by 17 income categories, ranging from "less than 5,000" to "$200,000 or more". The CTPP Part 1, Table 64, provides data by 25 income categories (+1 category for "total households) also ranging from < $5,000, to "$150,000 or more". The CTPP has better details in income categories less than $50,000, in increments of $2,500. This compares to SF3 which increments income categories by $5,000 ranges. So, if you really wanted to have data on "households less than $27,500" then you should use the CTPP. The other major benefit of the CTPP is that these detailed household income categories are cross-classfiied by various other variables, including person in household (Table -64), the number of workers in household (Table 1-66), and by the number of vehicles in the household (Table 1-67). These are valuable if you are examining very small area geography information for possible cross-classification travel models, say, shop/other trips (or tours) by household size by income level, etc. The major "cost" of using the CTPP is the independent rounding of cell values inflicted on the part 1 tables. So, the sum of the households by the 25 income categories may not precisely match the "total households" also provided in the same CTPP table. This is an annoyance, but can be overcome by normalizing (adjusting) the CTPP cell values to either match the "CTPP total households" value, or the "SF3 total households" which are not subject to the rounding nonsense. My recommendation would be to use the CTPP, and then normalize the CTPP tables to the SF1 precise count of households for your TAZ. This means you need a precise correspondence file of blocks-to-TAZ, so that you can "roll-up" the SF1 counts of 100% short form data (total pop, household pop, households, pop by race/ethnicity/age/sex) to your TAZes. Note that neither the SF1 or SF3 files were subjected to the rounding rules. This means that the numbers should always add up precisely to the same number. Hope this helps, Chuck Purvis, MTC - SF Bay Area I am compiling income data for our region at the TAZ level and have 2 sources to choose from, the CTPP TAZ income data by place of residence or the SF3 block group income data modified to fit our DASZ structure. I wonder if I could get some thoughts on which source might best represent a 2000 snapshot by TAZ. Thank you, Kendra Kendra Watkins Senior Data Analyst Mid-Region Council of Governments 809 Copper Ave. NW Albuquerque, NM 87102 (505) 724-3601 kwatkins(a)mrcog-nm.gov