Technical Issues Associated with the
American Community Survey
Lisa Neidert
NPC Poverty/American Community Survey
Workshop
June 22-26, 2009
Statistical Notes
 Reference purposes
 Do not need to use for presentation on Friday
 Often ignored for overview talks
 Often ignored, unless required by reviewer
 Statistical issues are not ACS-specific
 Census Bureau is more sensitive to statistical issues
in 2008 than they were in 2000, 1990


Confidentiality
Standard errors/Margins of Error in ACS, but not census
products
 Resources:
 http://www.psc.isr.umich.edu/dis/acs/handouts/Compa
ss_Appendix.pdf
 http://www.psc.isr.umich.edu/dis/acs/dataanalysis/Usi
ngReplicateWeights.html
Technical Appendices
 Each Compass guide has the same
glossary and set of appendices
 http://www.psc.isr.umich.edu/dis/acs/han
douts/Compass_Appendix.pdf
Big Picture
 Appendix 3 – Definitions

Standard Errors
 How

to get a SE from MOE
Margin of Error
 Reported
with summary tabulations
 How to change from 90% to 95%; 99%


Confidence Interval
Coefficient of Variation
 Recommendations
Coefficient of Variation
 CV = Standard Error/Population Estimate

Note: Need to recover SE (Appendix 3)
 The smaller the CV the more reliable the
estimate is
 Preferable that CV < 10%
 If using a proportion, the closer the proportion is
to 0, the more unstable the CV is
Coefficient of Variation . . .
 1-year estimate vs 3-year estimate
 CV will be 70% larger for the 1-year estimate
 Decision is precision vs currency
 Use multi-year estimate if single year has CV >
10%
 If single year CV is > 50 percent, do not use
Minimum population thresholds
 Rule of thumb:

Population estimate (weighted) should be:
 >3,000
for 1-year
 >1,000 for 3-year
 >600 for 5-year
 [From older draft of Appendix 6]
Multiyear Estimates
 When comparing multiyear estimates,
use non-overlapping estimates

2005-2007 vs 2008-2010
 Do not compare a single year estimate
against a multiyear estimate


Both should be multiyear estimates
The single year estimate could be at the
peak or trough of an economic cycle vs the
more moderated multiyear estimate
Margins of Error for Derived
Estimates
 Summary data provide a margin of error
for every cell
 Researchers often combine cells


Geography like NYC community districts
comprised of multiple census tracts
Cells within a geography
 Combine
several age groups
Spreadsheet
 Illustrate New Derived MOE
 https://ctools.umich.edu/access/content/
group/34a72eab-daa4-4d14-80e09150727aed6c/Assignments/Technical%
20Appendix_Appendix_5.xls
Statistical Significance
 Appendix 4


ACS vs ACS
ACS vs Census
Replicate Weights
 To correct for the fact that the samples are not
random
 Census Bureau’s replicate weights are not
handled by statistical packages (as an option,
like JK or BRR)
 SAS program that has the algorithm
 https://ctools.umich.edu/access/content/gr
oup/34a72eab-daa4-4d14-80e09150727aed6c/Technical%20%20Statistical/sas_code_example.txt
Census Bureau recommendations
for replicate weights
 Garrett, B. Dale and Michael Starsinic. 2008.
“ACS Public Use Microdata Samples of 2005
and 2006 – How to Use Replicate Weights.”
Presentation at AAPOR Conference, New
Orleans, May 16, 2008.

https://ctools.umich.edu/access/content/group/3
4a72eab-daa4-4d14-80e09150727aed6c/Technical%20%20Statistical/How%20to%20Use%20PUMS%
20Replicate%20Weights.ppt
Theoretical Basis for Successive
Difference Model
 Fay, R. and Train, G. 1995. “Aspects of Survey
and Model-Based Postcensal Estimation of
Income and Poverty Characteristics for States
and Counties,” Proceedings of the Section on
Governmental Statistics, American Statistical
Association, pp. 154-159.