[Congressional Record Volume 145, Number 63 (Tuesday, May 4, 1999)]
[House]
[Pages H2612-H2615]
From the Congressional Record Online through the Government Publishing Office [www.gpo.gov]




                              CENSUS 2000

  The SPEAKER pro tempore. Under a previous order of the House, the 
gentlewoman from New York (Mrs. Maloney) is recognized for 5 minutes.
  Ms. MALONEY of New York. Mr. Speaker, once again I rise to point out 
that the experts support the use of scientific methods to correct the 
census for undercounts and overcounts. Yesterday the National Academy 
of Sciences released the first report from the fourth panel to review 
the Census Bureau's plans for the 2000 census. Yet again, the experts 
convened by the Academy endorsed the Census Bureau's plan to use 
science to evaluate and correct the census counts.
  At the end of 1998 the Census Bureau asked the National Academy of 
Sciences to convene a fourth panel to evaluate the Census Bureau's 
design for Census 2000. This independent panel, like the three that 
preceded it, has unequivocally stated that statistical methods work. 
The Academy panel stated yesterday that the design of the quality 
control survey represents, and I quote from the panel, ``good, current 
practice.'' In fact, the panel explained, and I quote:
  ``Because it is not possible to count everyone in a census, a post-
enumeration survey'' using modern scientific methods ``is an important 
element of census planning.''
  Currently the Census Bureau intends to use a post-enumeration survey 
entitled the Accuracy and Coverage Evaluation or A.C.E. The A.C.E. 
Survey was designed in light of the Supreme Court

[[Page H2613]]

decision regarding the use of statistical methods for the purpose of 
apportionment. Mr. Speaker, we are beginning to hear criticism of the 
A.C.E. This Academy report should finally put that criticism to rest.
  Yes, the A.C.E. is a different program in its design and size than 
the survey that had been planned for Census 2000 prior to the court 
case. Those who are critical of these differences are not reviewing the 
details of A.C.E. As the Academy reports, changes in sample size as a 
result of the Supreme Court decision, quote, should not affect the 
quality, end quote, of the results. In fact, the panel comments that 
since the Bureau will no longer be using statistical methods for 
apportionment, there is no need for the larger survey envisioned prior 
to the court decision. In addition, the Academy notes that it is 
appropriate to combine information across States.
  Mr. Speaker, yesterday's report demonstrates the professional 
community's continued strong support for the Census Bureau's plan for 
the year 2000 census. In 1994 the Academy issued its first report which 
laid the foundation for the current plans. In 1995 a second panel 
reviewing Census Bureau plans at the request of Congress in a 
bipartisan way reported that spending more money on traditional methods 
would not improve the accuracy of the counts or the census. Earlier 
this year a third panel of experts convened by the National Academy of 
Sciences said that it strongly supports the use of a quality control 
survey to correct for errors in the census.
  I support counting everyone. The National Academy of Sciences has 
stated for the fourth time that the best way to count the population is 
to use modern scientific methods. I am going to rely on the opinion of 
these independent, impartial scientists at the National Academy of 
Sciences. These experts say the plan devised by the professionals at 
the Census Bureau will give us the most accurate count. That is the 
plan that I support.
  If my colleagues agree with me, that we should count everyone, then 
they should join me in getting out of the way of the professionals at 
the Census Bureau. Let us let the professionals do what they are hired 
to do, count people, and let us let them do it in the best way they 
can. We should be encouraging the use of modern scientific methods in 
Census 2000, not preventing them.
  Mr. Speaker, I would like to put into the Record the report from the 
National Academy of Sciences, the fourth report that has come out in 
support of the use of modern scientific methods for the most accurate 
count in counting all Americans.
  The report referred to as is follows:
         National Research Council, Commission on Behavioral and 
           Social Sciences and Education,
                                      Washington, DC, May 3, 1999.
     Dr. Kenneth Prewitt,
     Director, U.S. Bureau of the Census,
     Washington, DC.
       Dear Dr. Prewitt: As part of its charge, the new Panel to 
     Review the 2000 Census offers this letter report on the 
     Census Bureau's plans for the design of the Accuracy and 
     Coverage Evaluation (ACE) survey, a new post-enumeration 
     survey. This survey is needed in light of the recent U.S. 
     Supreme Court ruling regarding the use of the census for 
     reapportionment.
       In general, the panel concludes that the ACE design work to 
     date is well considered. It represents good, current practice 
     in both sample design and post-stratification design, as well 
     as in the interrelationships between the two. In this letter 
     the panel offers observations and suggestions for the Census 
     Bureau's consideration as the work proceeds to complete the 
     ACE design.


                               background

       Because it is not possible to count everyone in a census, a 
     post-enumeration survey is an important element of census 
     planning. The survey results are combined with census data to 
     yield an alternative set of estimated counts that are used to 
     evaluate the basic census enumeration and that can be used 
     for other purposes. For 2000, an Integrated Coverage 
     Measurement (ICM) survey had been planned for evaluation and 
     to produce adjusted counts for all uses of the census.\1\ The 
     recent U.S. Supreme Court ruling against the use of sampling 
     for reapportionment among the states eliminates the need for 
     a post-enumeration survey that supports direct state 
     estimates, as was originally planned for the ICM survey. (The 
     state allocations of the ICM sample design deviated markedly 
     from a proportional-to-size allocation in order to support 
     direct state estimation. Specifically, the ICM design 
     required a minimum of 300 block clusters in each state.) 
     Alternative approaches are now possible for both sample and 
     post-stratification designs for the 2000 ACE survey. As a 
     result, the planned ACE post-enumeration survey will differ 
     in several important respects from the previously planned ICM 
     survey.
---------------------------------------------------------------------------
     \1\Footnotes at end of attachment to the letter.
---------------------------------------------------------------------------


          plans for ace sample and post-stratification design

       Our understanding of the current plans for the ACE survey 
     is based on information from Census Bureau staff.\2\ Building 
     on its work for the previously planned ICM, the Census Bureau 
     will first identify a sample of block clusters containing 
     approximately 2 million housing units and then will 
     independently develop a new list of addresses for those 
     blocks.\3\ In a second stage, a sample of block clusters will 
     be drawn from the initial sample to obtain approximately 
     750,000 housing units, which was the number originally 
     planned for the ICM. (Larger block clusters will not be drawn 
     in their entirety; they will first be subsampled to obtain 
     sampling units of 30-50 housing units. Because the costs of 
     interviewing are so much greater than the costs of listing 
     addresses, this subsampling approach allows the interviewed 
     housing units to be allocated in a more effective manner.) 
     Finally, in a third stage, a sample of block clusters will be 
     drawn from the second-stage sample to obtain the 
     approximately 300,000 housing units required for the ACE 
     sample. The target of 300,000 housing units for the ACE, 
     which may be modified somewhat, will be based on a new set of 
     criteria that are not yet final.
       The Census Bureau is considering three strategies for 
     selection of the 300,000 ACE subsample from the 750,000 
     sample: (1) reducing the sample proportionately in terms of 
     state and other block characteristics from 750,000 to 
     300,000; (2) reducing the sample by using varying proportions 
     by state; or (3) differentially reducing the sample by 
     retaining a higher proportion of blocks in areas with higher 
     percentages of minorities (based on the 1990 census).\4\ 
     These options for selection of the 300,000 ACE housing units 
     from the 750,000 units first selected will be carefully 
     evaluated. The plans include three evaluation criteria for 
     assessing the options: (a) to reduce the estimated 
     coefficients of variation for 51 post-stratum groups (related 
     to the 357-cell post-stratification design discussed below); 
     (b) to reduce the differences in coefficients of variation 
     for race/ethnicity and tenure groups; and (c) to reduce the 
     coefficients of  variation for estimated state totals. 
     (Option (3) above is motivated by criterion (b)). Without 
     going into detail, it is also useful to mention that the 
     Census Bureau has instituted a number of design changes 
     from the 1990 post-enumeration survey for the ACE that 
     will reduce the variation in sampling weights for blocks, 
     which will reduce the sensitivity of the final estimates 
     to results for individual blocks. This represents a key 
     improvement in comparison with the 1990 design.
       The current plan to produce post-strata involves 
     modification of the 357-cell post-stratification design 
     suggested for use in 1990-based intercensal estimation. 
     Current modification under consideration by the Census Bureau 
     include expansion of the geographic stratification for non-
     Hispanic whites from four regions to nine census divisions, 
     adding a race/ethnicity group, changing the definition of the 
     urbanicity variable, and adding new post-stratification 
     factors, such as mail return rate at the block level. 
     Logistic regression, modeling inclusion in the 1990 census, 
     is being used to help identify new variables that might be 
     useful, as well as to provide a hierarchy of the current 
     post-stratification factors that will be used to guide 
     collapsing of cells if that is needed. (In comparison, the 
     analysis that generated the 357-cell post-stratification was 
     based on indirect measures of census undercoverage, such as 
     the census substitution rate.)
       The Census Bureau plan demonstrates awareness of the 
     interaction of its modification of the 750,000 housing unit 
     sample design with its modification of the 357 post-strata 
     design. (On the most basic level, the sample size allocated 
     to each post-stratum determines the variance of its 
     estimate.) The plan also makes clear that even though much of 
     the information used to support this modification process 
     must be based on the 1990 census, it is important that the 
     ultimate design for the ACE survey (and any associated 
     estimation) allows for plausible departures from the 1990 
     findings. For example, significant differences between the 
     1990 and 2000 censuses could stem from the change in the 
     surrounding block search for matches, the planned change in 
     the treatment of ACE movers, or changes in patterns and 
     overall levels of household response.


                       observations and comments

     Sample design to select the 300,000 housing units
       Because of the need to keep the ACE on schedule by 
     initiating resource allocations that support the independent 
     listing of the 2 million addresses relatively soon, as well 
     as the need to avoid development and testing of new computer 
     software, the Census Bureau has decided to subsample the 
     300,000 ACE housing units from the 750,000 housing units of 
     the previously planned ICM design. The panel agrees that 
     operational considerations support this decision.

[[Page H2614]]

       The cost of the constraint of selecting the 300,000 ACE 
     housing units from the 750,000 ICM housing units, in 
     comparison with an unconstrained selection of 300,000 housing 
     units, is modest. While the constrained selection will likely 
     result in estimates with somewhat higher variances, the panel 
     believes that careful selection of the subsample can limit 
     the increase in variance to that it will not be 
     consequential. (By careful selection, the panel means use of 
     the suggested approaches of the Census Bureau, or new or 
     hybrid techniques, to identify a method that best satisfies 
     the criteria listed above.) This judgment by the panel, 
     although not based on a specific analysis by itself or the 
     Census Bureau, takes into account the fact that a large 
     fraction of  the 750,000 housing units of the ICM design are 
     selected according to criteria very similar to those 
     proposed for the ACE design.
       In addition, the panel notes that the removal of the 
     requirement for direct state estimates permits a substantial 
     reduction in sample size from the 750,000 ICM design in 
     sparsely populated states, for which ACE estimates can now 
     pool information across states. As a result the ACE design 
     could result in estimates with comparable reliability to that 
     of the previously planned, much larger ICM design.
       Given the freedom to use estimates that borrow strength 
     across states, the final ACE sample should reduce the amount 
     of sampling within less populous states from that for the 
     preliminary sample of 750,000 housing units. However, there 
     is a statistical basis either for retaining a minimum ACE 
     sample in each state, or what is nearly equivalent, for 
     retaining a sample to support an ACE estimate with a minimum 
     coefficient of variation. The estimation now planned for the 
     ACE survey assumes that there will be no important state 
     effects on post-stratum undercoverage factors. In evaluating 
     the quality of ACE estimates, it will be important to 
     validate this assumption, which can only be done for each 
     state if the direct state estimates are of sufficient quality 
     to support the comparison, acknowledging that for some of 
     these analyses one might pool data for similar, neighboring 
     states. (Identification of significant state effects would 
     not necessarily invalidate use of the ACE estimates for 
     various purposes but would be used as part of an overall 
     assessment of their quality.)
       This validation could take many forms, and it is, 
     therefore, difficult to specify the precise sample size or 
     coefficient of variation needed. We offer one approach the 
     Census Bureau should examine for assessing the adequacy of 
     either type of standard. Using the criteria for evaluating 
     alternative subsample designs (i.e., the estimated 
     coefficients of variation for 51 post-stratum groups, the 
     differences in coefficients of variation for race/ethnicity 
     and tenure groups, and the coefficients of variation for 
     state totals), the Census Bureau should try out various state 
     minima sample sizes to determine their effects on the 
     outputs. It is possible that a moderately sized state minimum 
     sample can be obtained without affecting the above 
     coefficients of variation to any important extent. There are 
     a variety of ways in which the assumption of the lack of 
     residual state effects after accounting for post-stratum 
     differences could be assessed, including regression methods. 
     We encourage the Census Bureau to consider this important 
     analytic issue early and provide plans for addressing it 
     before the survey design is final.
       The panel makes one additional point on state minima. The 
     state minima will support direct state estimates that will be 
     fairly reliable for many states. The Census Bureau should 
     consider using the direct state estimates not only for 
     validation, but also in estimation--in case of a failure of 
     the assumption that there will be no important state effects 
     on undercoverage factors. Specifically, the Census Bureau 
     should examine the feasibility of combining the currently 
     planned ACE estimates at the state level with the direct 
     state estimates, using estimated mean-squared error to 
     evaluate the performance of such a combined estimate in 
     comparison with the currently planned estimates. We 
     understand that the necessity of prespecification of census 
     procedure requires that the Census Bureau formulate an 
     estimation strategy prior to the census, which adds urgency 
     to this issue.
       Finally, the panel has two suggestions with respect to the 
     criteria used for assessing the ACE sample design. First, 
     there should be an assessment of the quality of the estimates 
     for  geographical areas at some level of aggregation below 
     that of states, as deemed appropriate by the Census 
     Bureau. (This criterion is also important for evaluating 
     the ACE post-stratification design, discussed below.) 
     Second, the importance of equalizing the coefficients of 
     variation for different post-strata depends on how 
     estimates for specific post-strata with higher 
     coefficients of variation for post-strata that do not have 
     much effect have less need to be controlled, assuming that 
     the estimates for these post-strata do not have other 
     uses.
     Post-stratification plans
       The 1999 census adjusted counts used 1,392 post-strata, but 
     post-production analysis for calculating adjusted counts for 
     intercensal purposes resulted in the use of 357 post-strata. 
     The panel believes that the use of these 357 post-strata (and 
     the hierachy for collapsing post-stratification cells) was a 
     reasonable design for 1990, and that, in turn, the 1990 
     design is a good starting point in determining the post-
     strata to be used in the 2000 ACE. The Census Bureau is 
     considering four types of modifications to the 357 post-
     strata design, although it has not yet set the criteria for 
     evaluating various post-stratification designs. Logistic 
     regression will be used to identify new variables and 
     interactions of existing variables that might be added to the 
     post-stratification. Finer post-strata have the advantage of 
     greater within-cell homogeneity, potentially producing better 
     estimates when carried down to lower levels of geographic 
     aggregation. Some gains with respect to the important problem 
     to lower levels of geographic aggregation. Some gains with 
     respect to the important problem of correlation bias might 
     also occur. However, stratifying on factors that are not 
     related to the undercount will generally decrease the 
     precision of undercount adjustments. The tradeoff between 
     within-cell homogeneity and precision needs to be assessed to 
     undermine whether certain calls should be collapsed and 
     whether additional variables should be used.
       It is also important to examine the effects of various 
     attempts at post-stratification on the quality of substate 
     estimates, especially since certain demographic groups are 
     more subject to undercoverage, and so substate areas with a 
     high percentage of these groups will have estimates with 
     higher variances. (This argument is based on the fact that, 
     as in the binomial situation, the mean and the variance of 
     estimated undercounts are typically positively related.) We 
     believe it is extremely important that analysis at substate 
     levels of aggregation be conducted to inform both the sample 
     design and the post-stratification scheme. Furthermore, this 
     issue needs to be studied simultaneously with that of the 
     effect of the design and post-stratification on the post-
     stratification on the post-stratum estimates. The fact that 
     analysis of substate areas appears in both sample design and 
     post-stratification design is an indication of the important 
     interaction between these two design elements and justifies 
     the need for studies of them to be carried out 
     simultaneously. The panel encourages the Census Bureau to 
     work on them at the same time.
       The panel notes that the decision to use a modification of 
     the 357-strata system from 1990 for the ACE post-
     stratification design will probably not permit many checks 
     against estimates from demographic analysis that use direct 
     estimates from ACE. This limitation may increase the 
     difficulty of identifying the precise source of large 
     discrepancies in these comparisons. However, the panel does 
     not view this is a reason not proceed, since the  precision 
     of direct estimates at the finest level of detail of post-
     stratification (using 1,392 strata in this context) could 
     make such comparisons more difficult to interpret, and the 
     estimates from demographic analysis are not extremely 
     useful for this purpose (except for blacks, and then only 
     nationally).
       As work on both the sample design and post-stratification 
     design progresses, the Census Bureau should not rely entirely 
     on information from the 1990 census: substantial differences 
     might occur between the 1990 and the 2000 censuses that would 
     lead to either a sample design or a post-stratification 
     design that was optimized for 1990 but that might not perform 
     as well in 2000. Instead, the Census Bureau should use a 
     sample design that moves toward a more equal probability 
     design than 1990 information would suggest. Similarly, the 
     Census Bureau, using whatever information is available since 
     1990 on factors related to census undercoverage, should 
     develop a post-stratification design that will perform well 
     for modest departures from 1990.
       Finally, when considering criteria for both sample design 
     and post-strata, it is important to keep in mind that the 
     goal of the census is to provide estimated counts for 
     geographic areas as well as for demographic groups. Since the 
     use of equal coefficients of variation for post-strata will 
     not adequately balance these competing demands, the Census 
     Bureau will need to give further attention to this difficult 
     issue. The balancing of competing goals is not only a post-
     stratification issue, but also a sample design issue. For 
     example, if block clusters that contain large proportions of 
     a specific demographic group are substantially 
     underrepresented in the ACE sample, the performance of the 
     estimates for some areas could be affected.
     Documentation
       Given the importance of key decisions and input values for 
     the ACE design, it is important that they be documented. In 
     particular, the Census Bureau should produce an accessible 
     document in print or in electronic form that (1) gives the 
     planning values for state-level, substate level, and post-
     stratum level variances resulting from the decisions for the 
     sample and post-stratification designs and (2) provides the 
     sampling weights used in the ACE selection of block clusters.


                                summary

       From its review of the Census Bureau's current plans for 
     design of the ACE survey, the panel offers three general 
     comments;
       The panel concludes that the general nature of the Census 
     Bureau's work on the ACE design represents good, current 
     practice in sample design and post-stratification design and 
     their interactions.
       The panel recognizes that operational constraints make it 
     necessary for the Census Bureau to subsample the ACE from the 
     previously planned ICM sample. The subsampling, if done 
     properly, should not affect the

[[Page H2615]]

     quality of the resulting design if compared with one that 
     sampled 300,000 housing units that were not a subset of the 
     750,000 housing units previously planned for the ICM.
       The panel believes that removal of the constraint to 
     produce direct state estimates justifies the substantial 
     reduction in the ACE sample size from the ICM sample size. 
     The planned ACE could result in estimates with comparable 
     reliability to that of the larger ICM design.
       The panel offers three suggestions for the Census Bureau as 
     it works to finalize the ACE design, some of which the Census 
     Bureau is already considering: (1) a method for examining how 
     large a state minimum sample to retain; (2) some 
     modifications in the criteria used to evaluate the ACE sample 
     design and post-stratification, namely, lower priority for 
     coefficents of variation for excessively detailed post-strata 
     and more attention to coefficents of variation for substate 
     areas; and (3) a possible change in the ACE estimation 
     procedure, involving use of direct state estimates in 
     combination with the currently planned estimates. In 
     addition, the Census Bureau should fully document key 
     decisions for the ACE design.
       The panel looks forward to continuing to review the ACE 
     design and estimation as the Census Bureau's plans are 
     further developed. The panel is especially interested in the 
     evolving plans for post-stratification design, including the 
     use of logistic regression to identify additional post-
     stratification factors; plans for the treatment of movers in 
     ACE; and the treatment of nonresponse as it relates to 
     unresolved matches in ACE estimation. In addition, after data 
     have been collected, the panel is interested in the 
     assessment of the effect of nonsampling error on ACE 
     estimation and the overal evaluation criteria used to assess 
     the quality of ACE estimates.
       We conclude by commending you and your staff for the 
     openness you have shown and your willingness to discuss the 
     ACE survey and other aspects of the planning for the 2000 
     census.
           Sincerely,
                                          Janet L. Norwood, Chair,
                                  Panel to Review the 2000 Census.

       Attachment: Panel Roster.

                    Panel to Review the 2000 Census

       Janet L. Norwood (Chair), Urban Institute, Washington, DC
       Robert M. Bell, RAND, Santa Monica, CA
       Norman M. Bradburn, National Opinion Research Center, 
     Chicago, IL
       Lawrence D. Brown, Department of Statistics, University of 
     Pennsylvania
       William F. Eddy, Department of Statistics, Carnegie Mellon 
     University
       Robert M. Hauser, Department of Sociology, University of 
     Wisconsin
       Roderick J.A. Little, School of Public Health, University 
     of Michigan
       Ingram Olkin, Department of Statistics, Stanford University
       D. Bruce Petrie, Statistics Canada, Ottawa, Ontario
       Andrew A. White, Study Director
       Constance F. Citro, Senior Program Officer
       Michael L. Cohen, Senior Program Officer

                               Footnotes

     \1\ See National Research Council (1999), Measuring a 
     Changing Nation: Modern Methods for the 2000 Census. Michael 
     L. Cohen, Andrew A. White, and Keith F. Rust, eds., Panel to 
     Evaluate Alternative Census Methodologies, Committee on 
     National Statistics, National Research Council. Washington, 
     D.C.: National Academy Press.
     \2\ See Kostanich, Donna, Richard Griffin, and Deborah 
     Fenstermaker (1999), Accuracy and Coverage Evaluation Survey: 
     Plans for Census 2000. Unpublished paper prepared for the 
     March 19, 1999, meeting of the Panel to Review the 2000 
     Census. U.S. Bureau of the Census, Department of Commerce, 
     Washington, D.C.
     \3\ The use of the term block cluster refers to the adjoining 
     of one or more very small blocks to an adjacent block for the 
     purpose of the ACE sample design. Large blocks often form 
     their own block clusters.
     \4\ The Census Bureau is aware that mixtures of strategies 
     (2) and (3) are also possible, although such mixtures are not 
     currently being considered.

                          ____________________