There is a document published by the Census Bureau every year. For 2011 - Source and Accuracy of Estimates for Income, Poverty, and Health Insurance Coverage in the United States: 2011
It says "Be careful":
Comparability of Data.
Data obtained from the CPS and other sources are not entirely comparable. This results from differences in interviewer training and experience and in differing survey processes. This is an example of nonsampling variability not reflected in the standard errors. Therefore, caution should be used when comparing results from different sources.
Data users should be careful when comparing estimates for 2011 in Income, Poverty, and Health Insurance Coverage in the United States: 2011 (which reflect Census 2010‐based controls) with estimates for 1999 to 2010 (from March 2000 CPS to March 2011 CPS), which reflect Census 2000‐based controls, and to 1992 to 1998 (from March 1993 CPS to March 1999 CPS), which reflect 1990 census‐based controls. Ideally, the same population controls should be used when comparing any estimates.
In reality, the use of the same population controls is not practical when comparing trend data over a period of 10 to 20 years. Thus, when it is necessary to combine or compare data based on different controls or different designs, data users should be aware that changes in weighting controls or weighting procedures can create small differences between estimates. See the discussion following for information on comparing estimates derived from different controls or different sample designs.
It says "Be careful":
Comparability of Data.
Data obtained from the CPS and other sources are not entirely comparable. This results from differences in interviewer training and experience and in differing survey processes. This is an example of nonsampling variability not reflected in the standard errors. Therefore, caution should be used when comparing results from different sources.
Data users should be careful when comparing estimates for 2011 in Income, Poverty, and Health Insurance Coverage in the United States: 2011 (which reflect Census 2010‐based controls) with estimates for 1999 to 2010 (from March 2000 CPS to March 2011 CPS), which reflect Census 2000‐based controls, and to 1992 to 1998 (from March 1993 CPS to March 1999 CPS), which reflect 1990 census‐based controls. Ideally, the same population controls should be used when comparing any estimates.
In reality, the use of the same population controls is not practical when comparing trend data over a period of 10 to 20 years. Thus, when it is necessary to combine or compare data based on different controls or different designs, data users should be aware that changes in weighting controls or weighting procedures can create small differences between estimates. See the discussion following for information on comparing estimates derived from different controls or different sample designs.
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