RE: [CTPP] [ctpp-news] Demographic Analysis for Block Groups - Decennial Census vs. ACS 5 Year Estimates

Very valid points made here. And while we are slightly off topic, I wanted to add that the Census website has a very good online resource for the ACS that will tell you the sample size and data quality here: http://www.census.gov/acs/www/methodology/sample_size_and_data_quality/ In Census 2000 the long form was sent to approximately 1 in 6 households. With the ACS it is probably more like 1 in 60 or 1 in 100, depending on the area. Also, remember that the ACS multi-year data is an average of all the surveys taken across that 5-year (or 3-year or even the 1-Year) period. It is not a single point in time like the Decennial census is. So the two really should not be compared, though the ACS can give a good idea of the characterstics of the population across that time frame, it does not describe the population at that point in time. If you want to compare 5-year ACS data, you'll need to compare them in non-overlapping segments - so the 2005-2009 5 year should not be compared to the 2006 to 2010 data that will come out the end of this year as they will have overlapping data. You'd need to compare 2005-2009 5year with 2010-2014. Though I imagine many people will do just that. My point is, when using the ACS data it is very important to understand the data and, especially, understand its limitations. The ACS website does have a lot of good information and I highly recommend that anyone thinking about using the ACS for any sort of analysis get familiar with it and possibly read through the "Handbook for Data Users" on the ACS website. ============================= Jami Garrison, GISP Socioeconomic Research Program Manager   Maricopa Association of Governments 302 N 1st Ave, Ste 300 Phoenix, AZ 85003 (602) 452-5006 jgarrison(a)azmag.gov -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Jonathan Lupton Sent: Wednesday, April 06, 2011 2:44 PM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] [ctpp-news] Demographic Analysis for Block Groups - Decennial Census vs. ACS 5 Year Estimates Ms. Cogburn: I can't address all of your concerns, but I can say I'd be careful with the 5-yr ACS at the BG level. The sample size is just too small, and margins of error too great. I agree with Ms. Becker that the old long form data probably had large errors at the small-geography level too, but the nice thing is they didn't tell us the margins of error! I have found the ACS useful and reliable at larger areas of geography, but the 5-yr product has shown signs of inaccuracy in our region. For example, one of our towns with a population of 2,200 showed a median HH income trend that looked odd (sharply declining median household income from 2000 to the 2005-2009 period). It could be true, but the trend change is completely different from what LEHD's "On the Map" product showed for approximately the same time period (2003-2009), for the same town, on workforce earnings by place of residence. As I understand it, LEHD comes from a survey which, while not perfect, gets a sizeable chunk of the workforce, while ACS resident surveys leave lots of holes. Admittedly, there's an "apples and oranges" aspect to comparing ACS with LEHD, and median HH income with workforce earnings. I'd like to see more research on the respective advantages of ACS and LEHD. Summary: I'd treat the ACS five-year product with care for BGs until we have more experience with it. And, if you haven't already, you might want to fiddle with the LEHD's new version of "On the Map," it's got a high "wow" factor for quick place-based data analysis. Jonathan Lupton Research Planner Metroplan Little Rock AR -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Cogburn, Megan S Sent: Wednesday, April 06, 2011 2:58 PM To: ctpp-news(a)chrispy.net Subject: [CTPP] [ctpp-news] Demographic Analysis for Block Groups - Decennial Census vs. ACS 5 Year Estimates My name is Megan Cogburn and I am a Community Planner with the North Carolina Department of Transportation. My group is a part of the Project Development and Environmental Analysis branch and we are responsible for completing all of the NEPA documentation for bridge and highway projects statewide. Specifically, we prepare technical reports assessing potential project impacts on the human environment from the local/urban planning perspective. We currently use decennial Census data for our demographic analyses, however we are thinking of switching to use American Community Survey data to make our reports more current and since the American Community Survey has now replaced the traditional decennial Census long-form. However, it has come to our attention that ACS data is only available at the block group level for 5 Year Estimates (and not annually). Moreover, certain tables that were available for the 2000 Census are not available in the ACS 5 Year Estimates (such as household type by relationship, sex by employment status, and poverty status). Another glaring issue is that ACS 5 Year Estimates were just released in 2010, so there is no previous data to make historical comparisons. So, my question for the listserv is how other organizations are moving forward given the discrepancies between the two datasets. My group is trying to figure out where to get missing data, how to make historical comparisons, and also the best way to retrieve ACS 5-Year Estimates. A huge drawback for us is that we use block group data for multiple variables and this is only available for the 5 year estimates. In order to retrieve summary file data for block groups you have to use an Excel macro retrieval file that takes an extremely long time, download a massive file from their FTP site, or use the not so user friendly Data Ferret platform. Please advise! Megan Cogburn, MCRP Community Planner | Human Environment Unit NCDOT Project Development & Environmental Analysis e: mscogburn(a)ncdot.gov p: (919) 707-6062 f: (919) 212-5785 Email correspondence to and from this sender is subject to the N.C. Public Records Law and may be disclosed to third parties. _______________________________________________ ctpp-news mailing list ctpp-news(a)chrispy.net http://www.chrispy.net/mailman/listinfo/ctpp-news _______________________________________________ ctpp-news mailing list ctpp-news(a)chrispy.net http://www.chrispy.net/mailman/listinfo/ctpp-news