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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Summary

Since the successful transition from the long-form sample of the decennial census, the continuous American Community Survey (ACS) has become an invaluable resource for many stakeholders, particularly for meeting data needs for the nation, states, and cities and counties with large populations. However, due to inadequate sample sizes, a major challenge for the survey is producing estimates with adequate statistical precision for small geographic areas and small population groups. This challenge is a concern because of the unique role fulfilled by the long-form sample, and now the ACS, of providing data with a granularity that no other federal survey provides. In addition to the primary challenge of the precision of ACS estimates, this is also a good time to assess other aspects of the survey in order to identify opportunities for refinement based on the experience of its first few years.

The U.S. Census Bureau asked the Committee on National Statistics of the National Research Council (NRC) to convene a panel to provide input on ways of improving the ACS, focusing on two priority areas: identifying methods that could improve the quality of the data available for small geographic areas and population groups and suggesting changes that would increase the survey’s efficiency in responding to new data needs. As is frequently the case in the literature, the panel uses small area data to mean data for small domains, such as small geographic areas and small population groups.

The panel’s deliberations led to the formulation of three guiding principles that provide a framework for the discussions and recommendations in this report:

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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  • While comparisons to the decennial long-form survey provide a useful context for understanding the evolution of the ACS, the unique strength of the survey is not in replicating the long-form survey, but in meeting data needs that can best be addressed by a large national survey with the design characteristics of the ACS. The needs for small area data evolve and so do the methods and tools available for accomplishing the survey’s objectives.
  • How well the survey is meeting data needs for small administrative entities and population groups can only be truly assessed from the perspective of the broad range of stakeholders who use the data. In the design of a successful survey, there is no substitute for a thorough understanding of data users’ needs.
  • Tradeoffs will have to be made. Some of these tradeoffs are inevitable choices between competing survey design objectives (such as speed, accuracy, and level of detail). Other tradeoffs are imposed by resource limitations, particularly a sample size that is insufficient for producing adequately precise data for all small geographic areas and groups. Given the role of the ACS as a national resource, design decisions, such as the optimal allocation of sample among geographic areas in order to improve the precision of the estimates, are not simply statistical questions: they also involve policy decisions. The panel was not charged with assessing these matters from a policy perspective, but nonetheless emphasizes that a solid understanding of stakeholder needs is necessary for informed policy decisions.

Close collaboration with data users is essential to ensure that as refinements to the survey are considered going forward, the decisions are informed by stakeholder input. Although an ACS Data User Group (ACS DUG) was recently formed and has become an active platform for information exchange related to the data, the ACS DUG is not tasked with providing formal data user input to the Census Bureau. A standing group that is available to provide feedback on the survey and the data from a stakeholder perspective could provide highly valuable long-term benefits and at very little cost to the Census Bureau. The panel thus offers an overarching priority recommendation.

RECOMMENDATION 1: As a priority, the Census Bureau should establish a formal, institutionalized, standing group to provide ongoing data user input on decisions related to the American Community Survey, and this standing group should include representation of data user organizations.

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

SAMPLE DESIGN AND PRECISION OF ESTIMATES

Some degree of reduction in the precision of the estimates relative to the long-form sample has always been viewed as the tradeoff for the benefits provided by annual ACS updates. However, budget constraints have affected sample sizes so that the small area data are unusable from the perspective of many stakeholders at the local level. After exploring options to address this issue, the Census Bureau recently instituted a sample reallocation program that shifts the sample among census tracts to make the coefficients of variation (CVs) more nearly equal for tracts and for political and administrative areas.

Although it is understandable that the Census Bureau would want to reduce the largest tract-level CVs, it is not clear whether a consistent policy rationale guides this approach. Under current overall sample size constraints, the sample reallocation has limited ability to raise the precision to acceptable levels in small tracts, while it creates inefficiencies in the geographic aggregation of estimates, a strategy the Census Bureau has been recommending to users in order to deal with concerns about precision.

The Census Bureau has also recently increased the nonresponse sampling rate to 100 percent in selected areas, but without providing a clear rationale for this change. This change may cause the allocation of data collection resources in some of the smallest governmental units to be inefficient.

Although the panel does not recommend any immediate changes to the sample design, it is essential to integrate policy considerations into all research on the ACS design. This will help ensure that the needs of data users are being met and that the design of the survey is optimally cost efficient.

RECOMMENDATION 2: Future sample redesigns of the American Community Survey should consider whether there are explicit rationales based on identified data needs that justify deviations from proportional allocation of sample. Due regard should be given to the effects of reallocation on estimates for policy-relevant small geographic areas and nongeographically defined small groups.

RECOMMENDATION 3: Efforts to improve the precision of the American Community Survey estimates for specific small governmental units should be focused on increasing the initial designated sample size while maintaining the optimal nonresponse sampling rate instead of increasing the subsampling rate to 100 percent.

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

DATA COLLECTION METHODS

To maximize the efficiency of the data collection operations, the ACS uses four data collection modes: mail, Internet, telephone, and personal visit. The Census Bureau has also begun research on adaptive design techniques that could be incorporated into the data collection operations to increase efficiencies in fieldwork management. These efforts are promising, but they are greatly hindered by the lack of granularity in the way the Census Bureau tracks data collection costs, particularly by mode. What is needed is a system that can more precisely track costs to inform research and decisions on optimizing data collection operations, and the panel believes that implementing such a system is the most critical next step from a survey operations perspective. Although this step will undoubtedly involve some up-front costs due to changes or additions needed to the current survey management systems, the long-term payoff for a survey of the scale of the ACS is likely to be significant.

RECOMMENDATION 4: As a priority, the Census Bureau should develop systems for tracking American Community Survey data collection costs as precisely as possible, overall and by data collection mode.

Although the Census Bureau’s resources for research projects are limited, continuous evaluation of data collection approaches is needed because technologies and methods that can increase efficiency, improve data quality, and reduce respondent burden are constantly evolving. In the panel’s view, at least the initial stages of such evaluations are of relatively low cost and worthwhile investments that can translate into savings and improvements to the survey, for both respondents and data users, in the long run. The recommendations below fall into this category.

RECOMMENDATION 5: Taking into account cost and yield and their variation across areas, the Census Bureau should periodically evaluate the optimal subsampling rate for the American Community Survey, as well as the number of follow-ups in each mode.

RECOMMENDATION 6: The Census Bureau should evaluate the possibility of improving the American Community Survey’s accuracy at a fixed cost by truncating nonresponse follow-up or using modeling techniques to replace some of the nonresponse follow-up, particularly for the more expensive data collection modes.

RECOMMENDATION 7: The Census Bureau should conduct research on potential ways of identifying cell phone numbers associated with

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

adult household members and instruct American Community Survey field interviewers in proper protocols for calling cell phone numbers, as needed.

RECOMMENDATION 8: The Census Bureau should continue to conduct research on how adaptive design techniques can benefit the American Community Survey.

RECOMMENDATION 9: The Census Bureau should continue to investigate the use of auxiliary data to develop nonresponse models for the American Community Survey.

RECOMMENDATION 10: The Census Bureau should conduct a thorough evaluation of potential mode effects on both data quality and nonresponse in the American Community Survey, focusing in particular on the newly introduced Internet mode.

RECOMMENDATION 11: The Census Bureau should conduct research to understand what types of devices are used by American Community Survey respondents to connect to the Internet and whether there are any associated data quality implications.

DATA PROCESSING AND ANALYSIS

The way data are processed can affect their quality and usefulness to users. Estimates produced based on the census long-form sample benefited from weights based on population controls available from the simultaneous census enumeration, but similarly high-quality weights are not available for the ACS at all levels of geography. Research is needed to improve population controls, especially when an area is affected by a major disaster, such as a hurricane. Such events can greatly increase local governments’ need for up-to-date and accurate data in the aftermath of the event, while simultaneously making the Census Bureau’s task of providing such data more difficult. Expanding collaborations with state, local, and tribal governments is not assumed to be cost neutral, but it could represent an important opportunity for the Census Bureau to demonstrate the survey’s usefulness to existing and new stakeholders in critical situations.

RECOMMENDATION 12: The Census Bureau should conduct research on how the decennial census can be used for controls for the American Community Survey at a finer level of geographic resolution than the controls currently used on an annual basis.

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

RECOMMENDATION 13: The Census Bureau should conduct research on the benefits of developing procedures and standards for the creation of controls for the American Community Survey that can be put in place in times of disasters or other disruptive events. The benefits of closer collaborations with state, local, and tribal governments should be explored for the development of controls in general and for crisis situations in particular.

Currently, most of the data review steps happen after a year’s worth of data are edited, imputed, and used to generate data products. Errors can be introduced during any stage of data preparation (such as weighting or imputation), and errors in fieldwork (such as the questionnaire being incorrectly administered by field representatives) are also unavoidable. Consequently, deferring review until a full year’s worth of data are collected can lead to situations in which it is too late to correct the problem and some estimates have to be suppressed. The panel believes that from a data processing perspective, implementing ongoing quality control and editing processes is the most important next step, and one that could translate into significant cost savings in the long run if these checks successfully prevent potential major errors from affecting a full year’s worth of data.

RECOMMENDATION 14: As a priority, the quality control and editing processes in the American Community Survey should be ongoing and as close to the data collection as possible, to ensure that problems are identified promptly and that their impact is minimized.

RECOMMENDATION 15: The Census Bureau should evaluate whether procedural changes might improve the efficiency of the American Community Survey quality control operations.

The use of administrative records is another area that could be explored to enhance data processing, and further research on small area and small domain estimation options is also needed. These research projects would require dedicated resources, but they have the potential of identifying approaches that could have long-term payoffs and enhance the survey’s value to data users.

RECOMMENDATION 16: The Census Bureau should coordinate efforts across units on research related to the potential use of administrative records, and when possible, the American Community Survey Office should build on the research being conducted in other units. Promising topics include the use of administrative records for adaptive design, as

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

sources of data for items on the questionnaire, and to enhance estimation in the post data collection stages. (See also Recommendation 26.)

RECOMMENDATION 17: The Census Bureau should continue its program of small area estimation using American Community Survey data, maintaining a balance of methodological research and development of production applications directed to current user needs, methods for univariate and multivariate estimation, and intramural and extramural research.

RECOMMENDATION 18: The Census Bureau should negotiate agreements with potential federal sources of auxiliary variables for small area estimation, allowing sharing of data for multiple developmental and production uses, with suitable protections of confidentiality. In particular, the Census Bureau should endeavor to broaden its data-sharing agreement with the Internal Revenue Service to facilitate statistical uses beyond those directly related to the Small Area Income and Poverty Estimates Program.

DATA DISSEMINATION

The ACS data products include tables that involve rates or proportions, typically expressed as percentages, and are accompanied by margins of error (MoEs). This method works well for some estimates, but it can be confusing and uninformative in other cases, especially for small proportions. Research is needed to improve the presentation of measures of uncertainty to users. Implementing any changes would require testing and a minor redesign of some of the user interfaces, which would not be cost neutral, but improved presentation of measures of uncertainty would increase the clarity and value of the information presented to users.

RECOMMENDATION 19: The Census Bureau should continue research into alternative approaches for constructing and presenting measures of uncertainty for the American Community Survey that are suitable for data from complex survey designs and with small proportions or samples, with the objective of rapidly adopting new methods without the defects apparent in current practice.

RECOMMENDATION 20: The data disseminated from the American Community Survey should include both interval estimates (confidence or credible intervals) and approximately unbiased variance estimates, although the latter become less important if a suitable system for aggregation of estimates is introduced. (See also Recommendation 24.)

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

Despite the apparent abundance of data products, many of the actual estimates cannot be made available to data users because of the sample size limitations. In addition to data suppression to protect respondent confidentiality, the 1- and 3-year data are also subject to filtering due to concerns about precision. Under current procedures, more data are filtered out than is necessary. Changing the filtering rules would require some redesign of dissemination systems and processes, but making more data available would further increase the usefulness of the survey to data users.

RECOMMENDATION 21: The Census Bureau should revise the suppression practices for the American Community Survey: rather than suppressing data due to concerns about lack of precision, users should be provided with access to all data that pass confidentiality review. The Census Bureau will have to be proactive about user education and provide adequate information about the precision of the data to enable users to decide whether the data are suitable for use to meet their specific analytic needs.

RECOMMENDATION 22: The Census Bureau should evaluate whether the data release population thresholds of 65,000 or more for 1-year estimates and 20,000 or more for 3-year estimates are still optimal for the American Community Survey. This question should be revisited periodically.

The ACS data products were initially intentionally designed to facilitate comparison to the census long-form sample data products, but the annual release of a very large volume of 1-, 3-, and 5-year tables is very resource intensive, and it is unclear how useful many of the tables are to users. While many of the panel’s recommended changes to dissemination methods are primarily targeted at enhancing user experience, there is an opportunity to scale back some forms of dissemination that may have become less useful over the years and direct the savings to providing other benefits to users.

RECOMMENDATION 23: The Census Bureau should evaluate whether the current range of tables produced provides optimal value to data users and whether the table production could be limited to a core set in order to allocate resources for other projects.

The MoEs associated with many of the estimates for small areas and groups can be very large, and data users are encouraged to aggregate estimates across geographic areas or population subgroups to improve precision. However, data users find performing these aggregations challenging, particularly because calculating the MoEs for the aggregated estimates is

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

not always straightforward. Developing a tool that assists with these calculations would be an enhancement that would greatly improve data users’ satisfaction with ACS data products and needs to be a priority.

In the long run, data users would also benefit from a query system that has more flexibility for performing analyses based on the underlying microdata. The panel acknowledges that the development of these tools would require a substantial investment of resources, but these types of features appear to be the most valuable to users. They might also have a long-term payoff for the Census Bureau in terms of stakeholder satisfaction and possibly increased use of the data, as well as substituting for the production of large numbers of prespecified tables.

RECOMMENDATION 24: As a priority, the Census Bureau should develop a tool that enables data users to aggregate geographies and collapse categories, as well as to calculate the standard errors for the new estimates. To support a greater range of analyses, a microdata access system with additional capabilities should also be considered. The American Community Survey (ACS) Office should take the lead in developing these tools, working in collaboration with other Census Bureau offices. The Census Bureau should also involve a working group of ACS data users, State Data Centers, and user interface experts from the early stages of the process.

MANAGING THE ACS CONTENT

The broad range of uses and nuances in data user needs raises difficult questions about how to prioritize demands for survey content without further increasing respondent burden. Managing the content is a balance between federally mandated functions and broader uses of the data, and it appears to be hindered by a lack of systematic, in-depth understanding of the range of uses. Although the Census Bureau has recently conducted a review of the ACS content based on federal uses of the data, to successfully manage the content of the survey it is important that the Census Bureau gain a solid understanding of the needs of the survey’s stakeholders in a much broader sense. The panel considers this a priority in the context of content management. The recommended standing group to provide ongoing data user input (see Recommendation 1) can also provide guidance in accomplishing this task.

RECOMMENDATION 25: As a priority, the Census Bureau should conduct a comprehensive evaluation of the needs for the specific items on the American Community Survey, including nonfederal uses of the data. The evaluation should center on the level of disaggregation at

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

which the data are needed as the primary criterion, and the criteria and processes used for the evaluation should be documented.

Research on the potential use of administrative records to replace items on the questionnaire is not a priority area among the administrative records research projects currently being pursued by the Census Bureau, but if viable options could be found for obtaining some of the data from sources other than the interviews, this would reduce respondent burden and potentially enable the ACS to accommodate other data needs on the questionnaire.

RECOMMENDATION 26: The Census Bureau should continue research on the possible use of alternative sources and estimation methods to obtain content that is now collected on the American Community Survey. Once a comprehensive evaluation of the data needs has been completed, for each of the items, the Census Bureau should evaluate whether the survey represents the best source for those data or if data from other sources could be considered as a substitute. Research on the availability of alternative sources and estimation methods for the data should be ongoing.

Given the unique and valuable role of the ACS as part of the nation’s statistical system, particularly in terms of its ability to produce small area data, the demand for new questions exceeds what the survey can reasonably accommodate. Consequently, implementing and following a systematic and transparent process for managing the survey’s content is essential to ensure that the utility of the survey is maximized. These low-cost investments can have substantial payoffs in the long run.

RECOMMENDATION 27: The Census Bureau should clarify the criteria and aim to follow as closely as possible the guidelines and processes that have been established for the American Community Survey for adding new questions and dropping existing ones. Ad hoc, off-cycle changes should be the exception, rather than the rule, and new questions added this way should go through the full process during the next scheduled cycle of revisions. In all cases, it is important to maintain transparency about how the decisions are made.

RECOMMENDATION 28: The Census Bureau should evaluate whether the scope and size of the current field test required as part of the process of adding a new question to the American Community Survey is optimal or whether a smaller scale pretest (and separate

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
×

guidelines) may be adequate for minor questionnaire changes, allowing the survey to be more responsive to data user needs without sacrificing quality. Whatever the scope of the changes, the process should be systematic and transparent, with the goal of ensuring that their potential impact is fully assessed.

Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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Suggested Citation:"Summary." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.
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The American Community Survey (ACS) was conceptualized as a replacement to the census long form, which collected detailed population and housing data from a sample of the U.S. population, once a decade, as part of the decennial census operations. The long form was traditionally the main source of socio-economic information for areas below the national level. The data provided for small areas, such as counties, municipalities, and neighborhoods is what made the long form unique, and what makes the ACS unique today. Since the successful transition from the decennial long form in 2005, the ACS has become an invaluable resource for many stakeholders, particularly for meeting national and state level data needs. However, due to inadequate sample sizes, a major challenge for the survey is producing reliable estimates for smaller geographic areas, which is a concern because of the unique role fulfilled by the long form, and now the ACS, of providing data with a geographic granularity that no other federal survey could provide. In addition to the primary challenge associated with the reliability of the estimates, this is also a good time to assess other aspects of the survey in order to identify opportunities for refinement based on the experience of the first few years.

Realizing the Potential of the American Community Survey provides input on ways of improving the ACS, focusing on two priority areas: identifying methods that could improve the quality of the data available for small areas, and suggesting changes that would increase the survey's efficiency in responding to new data needs. This report considers changes that the ACS office should consider over the course of the next few years in order to further improve the ACS data. The recommendations of Realizing the Potential of the American Community Survey will help the Census Bureau improve performance in several areas, which may ultimately lead to improved data products as the survey enters its next decade.

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