ACS vs Census populations at the ZCTA level

Gene Shackman over 10 years ago

Hi all

Just fyi, I downloaded
B01001, SEX BY AGE, Universe: Total population, 2008-2012 American Community Survey 5-Year Estimates
and compared it to
PCT3. SEX BY AGE. Universe: Total population. 2010 Census Summary File 2
both at the ZCTA level

Here is a comparison of the totals

ACS 2010 Census
State, Total 19,397,882 19,375,158
State, under 5 1,159,733 1,155,708

Pretty close you say? Well..... it is, at this level, but lets compare data from ZCTAs, looking at the category of under 5 (I use this age group a lot)
ZCTA .........ACS ..........2010 Census
10001........686.............624
10002........3271...........3620
10598........1260...........1481
11713........671.............702
11941........52...............98
12428........425............437
12429........0................11
12430........51..............67
13203........938...........1177
13208........2079.........1912
14456........952...........1042
14462.......18..............35
14464.......409............417

Well, in this non random sample, the numbers are generally in the same range at least. So if I'm just looking at population, at the ZCTA level, I'm not sure there is much advantage to using the ACS. Obviously, too, my sample isn't very random. At the state level, the ACS estimate is slightly larger than the 2010 Census estimate. But in most of the ZCTAs I chose (at least randomly to me), most of the 2010 Census estimates are larger than the ACS estimates.

I guess the question is, should I expect close correspondence between the ACS and Census 2010, and if not, why not.

Thanks

Gene
(sorry for the dots. I can't seem to get data tables lined up any other way)

Parents

Ed Simmons over 10 years ago

I think there is no good answer for "how much difference should I expect". I would expect the numbers to be close but I don't have a fomula to say what close is. But, I would check the margin of error if it is greatly different from the Census. Also, consider the area. Is changing quickly? Demographic swings usually are not that dramatic but it should be considered. Consider something more volatile like persons in poverty. If you looked at the 2010 ACS 5-year estimate, 3/5ths of the sample would be pre-Great Recession. You would intellectually know the number in poverty in the 2010 ACS 5-yr is lower than the actual number of persons in poverty in 2010. This is a long winded way of saying the 5 year ACS is what it is. Try not to anchor it or compare it to other 1-year data sets (at least not so closely) you'll just get a headache.
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Ed Simmons over 10 years ago

I think there is no good answer for "how much difference should I expect". I would expect the numbers to be close but I don't have a fomula to say what close is. But, I would check the margin of error if it is greatly different from the Census. Also, consider the area. Is changing quickly? Demographic swings usually are not that dramatic but it should be considered. Consider something more volatile like persons in poverty. If you looked at the 2010 ACS 5-year estimate, 3/5ths of the sample would be pre-Great Recession. You would intellectually know the number in poverty in the 2010 ACS 5-yr is lower than the actual number of persons in poverty in 2010. This is a long winded way of saying the 5 year ACS is what it is. Try not to anchor it or compare it to other 1-year data sets (at least not so closely) you'll just get a headache.
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