FOR IMMEDIATE RELEASE
                   WEDNESDAY, MARCH 12, 2003

Mark Tolbert III                                                CB03-CS.02
Public Information Office
(301) 763-3691/ 457-3620 (fax)
(301) 457-1037 (TDD)
e-mail: <2000usa@census.gov>
                         
     Statement of Census Bureau Director C. Louis Kincannon
         on Accuracy and Coverage Evaluation Revision II
                                                               
Context

  In conjunction with Census 2000, the Census Bureau conducted an Accuracy
and Coverage Evaluation (A.C.E.).  The Census Bureau intended to use the
estimates produced by the original A.C.E. to adjust the census for both
undercounts (omissions) and overcounts (erroneous enumerations).  In March
2001, the Census Bureau recommended against census adjustment because the
results of the initial A.C.E. were dramatically inconsistent with
Demographic Analysis, another independent measure of census coverage.

  During the summer of 2001, the Census Bureau re-evaluated the results of
this original A.C.E., and in October 2001 once again decided against
adjusting the decennial census.  In this instance, we cited the small size
of the estimated net undercount, and that there were only four estimates
of coverage developed in the course of the second evaluation and these
were at the national level.  During the course of the research for the
October 2001 decision, serious concerns emerged regarding the number of
duplicate and erroneous census enumerations that were found during the
course of the research.

  In response, the Census Bureau researchers conducted extensive,
groundbreaking research throughout 2002.  The Census Bureau, in effect,
"re-opened" the A.C.E. and without reentering the field, completed a new
coverage evaluation and adjustment using enhanced and sometimes new
procedures that were targeted to address specific error in both the census
and the coverage evaluation survey.

  The Census Bureau conducted this research, A.C.E. Revision II [pdf], 
to provide a more in-depth analysis of, and where possible corrections 
to, the estimates of census net coverage.  In addition, this research has 
allowed us to understand more fully the properties of the census, how to 
account properly for census coverage, and how to improve our planning for 2010.
 
The Findings from A.C.E. Revision II

  A.C.E. Revision II revealed a great deal of additional information about
the accuracy of the census and about the accuracy of our measures of
coverage evaluation. The decennial census is a complex process, involving
millions of operations and decisions that contribute to the overall
coverage and accuracy of the census, and it is not without error.  Among
the specific issues for which we must do additional research are residence
rules, the use of proxy data, as well as the quality of proxy data, and
procedures for identifying duplicates.

  A.C.E. Revision II results contain the following key findings:

    - Rather than an estimated net undercount of 3 million persons, there
      was an estimated net overcount of 1.3 million persons.  (This would 
      have been an estimated overcount of 3 million persons, except for 
      the application of an adjustment for correlation bias. Correlation 
      bias has been observed and measured in the past but was never 
      included in estimates of net census coverage.)
      - This includes a net overcount for Non-Hispanic White that is 
        statistically significant, as well overcounts in the Non-Hispanic 
        Asian and American Indian on Reservation populations that are not 
        statistically significant.
      - There was a net undercount, however, for Non-Hispanic Black that 
        is statistically significant.  A.C.E. Revision II results also 
        indicate net undercounts for the Hispanic, Hawaiian and Other 
        Pacific Islander, and the American Indian off Reservation 
        populations that are not statistically significant.   
      - There is also an estimated net overcount for children aged 0-9 
        that is statistically significant according to A.C.E. Revision II.  
    - There were at least 5.8 million duplicates that are now measured in 
      Census 2000. The March 2001 estimates dramatically underestimated 
      these duplicates, as well as duplicates in the survey.  
     
Decision and Future

  The Census Bureau believes that the estimates produced from A.C.E.
Revision II represent the most accurate assessment of Census 2000 coverage
to date, replacing the flawed results of the March and October 2001 A.C.E.
processes.  However, we still have technical concerns about the
limitations of the methodology and the data produced by A.C.E. Revision
II.  In fact, due to our concern regarding the effects of the adjustment
for correlation bias and the effect of synthetic adjustment on smaller
geographies, as well as other limitations, the Census Bureau reaffirms its
prior decision (October 2001) that the intercensal population estimates
will be based on the official Census 2000 results rather than on a
population base adjusted using revised estimates of census coverage.

  Concern and discussion of these limitations, as well as the limitations
of the census itself, was part of an extensive technical and scientific
process.  We reached a consensus in making the decision not to adjust the
intercensal estimates through open discussion and debate of the technical
merits of A.C.E. Revision II.

  This process also reaffirms our confidence in the decisions made in
March and October of 2001.  It is our consensus that there are serious
considerations that must be addressed in order to assess accurately
coverage for the decennial census and that those considerations cannot be
addressed in time to meet the deadline for redistricting.

  Finally, the Census Bureau will now move forward from Census 2000.  We
will use this research to improve the coverage of the decennial census and
coverage evaluation program for 2010. We will always bear in mind that the
decennial census belongs to the people of the United States and we will
seek the counsel of our stakeholders, especially our peers in the
scientific and policy community, as we plan for the future.

Attachment [pdf]