[CTPP] Known issues in CTPP Part 1

Attention: State DOT and MPO staff evaluating CTPP 2000, Part 1: I received a number of e-mails/phone calls since my last e-mail asking for staff to evaluate different levels of geography. Some of the common issues are: 1. CTPP Part 1 data will not agree with SF 1 or Redistricting (Full count data). The CTPP data are based on the census long form, and are subject to weighting, just like other sample surveys. The SF1 and Redistricting data are full counts, and are more accurate. The best source to do spot-checks on the CTPP data is SF3. 2. The count of households WILL NOT EQUAL Occupied Housing Unit counts (in general). This is because the all the household data in the census are derived by tabulating the "person weight" of the householder. Weights for occupied housing units are assigned based on housing unit counts. 3. Please be aware that all CTPP tables (except the mean, median, and standard deviation tables) are subject to the following rounding rules: 0 is kept as 0. 1-7 are rounded to 4 Anything above 7 is rounded to the nearest multiple of 5 (eg: 9 is rounded to 10, 17 is rounded to 15 etc) Columns for Totals in each table may not match the sum of the categories because Totals are rounded independently of the cells. For example: 0 vehicle households = 6 is rounded to 4 1 vehicle households =14 is rounded to 15 2 vehicle households=8 is rounded to 10 3 vehicle households=8 is rounded to 10 4 vehicle households=3 is rounded to 4. Total households=39 is rounded to 40 (and NOT 4+15+10+10+4 = 43 rounded to 45). The difference between the totals and the sum of the parts is substantial for tables with more than 30 cells. 4. Missing geography: Sometimes, a few TAZs or BGs may not show up in your geography/map viewer or tables. This is because geography are shown only if at least ONE table in CTPP has some values. This means that those TAZs or BGs that don't show up have NO population or households in them (based on long form data). 5. Wrong Column headers: We noticed that the CTPP Access Tool wrongly labels column headers for one dimensional tables - this error will be fixed for the final version. 6. MSA/CMSA names are wrong: We think that the names for MSA/CMSA or PMSAs are incorrect, and should be fixed in the final version. If you have issues DIFFERENT from the above 6, please call/e-mail me. Thank you! Nanda Srinivasan 202-366-5021