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Gemini Project Vision Document 

Gemini Project Steering Team 

Bureau of Labor Statistics 

April 16, 2010 

Last Revised: 

February 25, 2015 

The purpose of this document is to provide an overview of the Gemini Project. 

Gemini Project Mission 

With the Gemini Project, the U.S. Bureau of Labor Statistics (BLS) aims to redesign the Consumer 

Expenditure (CE) survey to improve data quality through a verifiable reduction in measurement error—

particularly error caused by underreporting. The effort to reduce measurement error will combat further 

declines in response rates by balancing any expected benefits of survey design changes against any 

potential negative effects on response rates. Any improvements introduced as part of the Gemini Project 

should not increase budgetary burden, but instead, should remain budget neutral. 

CE Survey Objectives and Uses 

By improving the quality of the CE estimates, the CE survey (comprised of the CE quarterly interview, or 

“CEQ,” and the CE diary, or “CED”) satisfy their primary purpose: maintaining the integrity of the 

expenditure weights used in the Consumer Price Index (CPI). Improved data quality and stable or 

increasing response rates enhance the usefulness of the CE data for both public and private users. In the 

Federal sphere, for example, the Bureau of Economic Analysis (BEA) uses the data in estimating Personal 

Consumption Expenditures (PCE), while the Bureau of the Census employs Consumer Expenditure 

Survey-based thresholds to produce experimental poverty statistics. Congressional committees also 

request special tabulations of the data on issues such as the potential impact of increases in the minimum 

wage. The academic community and research organizations use CE public-use microdata extensively in 

their analytical work, investigating topics such as consumption over a person’s lifecycle, trends in 

expenditure inequality, the impact of public policy proposals on spending by consumers, and the 

consumption behavior of consumer units given differences in socioeconomic and demographic 

characteristics. Private companies use both CE tabular data and CE microdata in marketing their products 

and services. They do this directly or through firms that purchase CE microdata to provide such analytical 

services. In addition, CE data are a recommended resource for prospective entrepreneurs developing their 

business plans. 
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Motivation for Redesign 

The design of the CE survey must be updated on an as-needed basis to address the effect of changes in 

society, technology, new consumer products, and spending methods on survey estimates. Without these 

updates, the CE survey will not be able to continue producing high quality expenditure estimates for users. 

Surveys today face well-known challenges that affect response rates, such as increasingly busy 

respondents, confidentiality and privacy concerns, competing surveys, controlled-access residences, and 

non-English-speaking households. The CE survey face unique challenges that directly influence the quality 

of the data collected. Presented in order of importance, the three most challenging issues for the CE 

survey are the evidence of measurement error in the survey data, environmental changes related to new 

technology and consumption behaviors, and the need for greater flexibility in the mode of data collection 

and ability to update data collection strategies. 

1. Measurement Error. From 1984 until the present, the ratios of aggregate expenditure 

estimates from the CE compared with PCE data from the National Accounts show a 

declining trend for a large number of spending categories, serving as evidence of 

underreporting. Similar findings from internal methodological studies and the 2008 CE 

Program Review Report present further evidence of a growing concern about the quality of 

reported data. Underreporting in the CE may result from perceived (and real) respondent 

burden due to survey length and complexity, panel or questionnaire conditioning, 

increasing telephone administration of a survey originally designed for personal visit 

interviews, proxy reporting by a single household member, recall effects stemming from a 

3-month reference period, and other sources of measurement error. 

2. Environmental Changes. As new technologies evolve and are adopted, the CE survey 

must adapt to account for the environmental changes that accompany technological 

innovation. The two most important changes are the transformation of respondent behavior 

and the emergence of new data collection options. For example, online purchases and 

automatic payments are two popular methods of payment, and questionnaire design and 

data collection methods may have to be adapted to better account for them. The 

availability of new technology for data collection, such as a web diary, a portable digital 

assistant (PDA) instrument, or financial-software-generated balance sheets, offers new 

opportunities by which to collect data. Additionally, respondents may expect to be able to 

respond to the survey online, a service which BLS does not currently offer. Furthermore, a 

different survey design may better capture certain types of expenditures, such as 
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automatically-billed payments. Finally, the impact of shopping at large general 

merchandise stores, such as Costco and Walmart, on expenditure reporting is not known, 

but the topic-specific design of the survey may not correspond well to purchases of a large 

variety of goods at a single store. A different survey design may be better suited for 

capturing such expenditures. 

3. Greater Flexibility. The CE needs greater flexibility for two main reasons: to enable CEQ 

interviewing in more than one mode and to allow for faster implementation of changes to the 

questionnaire or instrument. Regarding the first reason, a multimode design would allow 

data collection to be tailored to the needs of the respondent, and could help to address the 

environmental changes noted above. For example, respondents who have very little time, 

have difficulty keeping a CED diary, or do not want an interviewer in their home all have 

different ways of optimally reporting their data. Accordingly, they would be more likely to 

complete an interview using one mode over another. The second reason for greater 

flexibility is that, as currently designed, changing the computer-assisted personal 

interviewing (CAPI) instrument requires considerable lead time. Increased flexibility in the 

instrument would allow the program to be responsive to social and external changes 

without a major instrument restructuring. 

Reducing measurement error is the primary mission of the Gemini Project, but environmental changes are 

an increasingly important mechanism through which measurement error may be introduced to the survey. 

And greater flexibility in the ability to update or revise data collection strategies better positions the survey to 

quickly respond to these environmental changes over the long term. 

Furthermore, the consumer expenditures that the survey seeks to measure have changed 

considerably over the past 30 years, while the fundamental design of the survey has not. Although a 

number of smaller scale improvements have been incorporated into the survey design, including the 

transition to a CAPI instrument, these changes have not been made within a larger, more 

comprehensive framework of addressing identified survey weaknesses. 

BLS initiated survey redesign plans several years in advance of the target implementation date in 

order to account for the length of time needed to develop, evaluate, pilot test, and implement a largescale survey redesign. The overall timeline should not exceed 5 years for development and pilot 

testing, with a new survey in the field within 10 years. 
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Gemini Project Objectives 

The short-term objective of the Gemini Project was to develop a detailed roadmap for the redesign of the 

CE survey, which will promote improved expenditure estimates through a reduction in measurement error. 

The completed redesign roadmap describes the priorities, individual steps, timeframe, resource needs, and 

costs required for the development, pilot testing, evaluation, and implementation of a redesigned CE 

survey. The roadmap also guides the development and implementation of CE research studies throughout 

the Gemini Project lifecycle. 

The long-term objectives of the redesign initiative are to reduce measurement error, improve overall data 

quality, enhance the analytic value of CE data to users, and implement a new design that supports a 

greater operational flexibility to respond to changes in the interviewing environment. 

Finally, the costs of the redesigned survey cannot exceed current budget levels. Therefore, all proposed 

changes are subject to budgetary constraints, and implementation decisions will be considered in terms of 

priorities and trade-offs. To allow for an unpredictable budgetary environment, the planning document will 

address both a complete redesign of the CE survey as well as more limited modifications to the current 

design. 

Approach 

The Gemini Project is managed by a project leader and steering team, with guidance from an executive 

management group. The Gemini Project includes three stages of work. (The timeline of Stages 1 and 2 are 

outlined in Attachment 1.) Stage 1 focused on summarizing research to reduce measurement error in the 

process of redesigning the CE survey and consisted of five major steps: 

1. Establishing a chartered steering team to oversee project activities 

2. Creating a research project tracking system 

3. Defining data quality for CE 

4. Coordinating a series of information gathering events 

5. Proposing redesign models 

Multiple information-gathering meetings, conference sessions, forums, and workshops were conducted in 

Stage 1, including the following events: 

 Survey Redesign Panel Discussion, co-sponsored by the Washington Chapter of the American 

Association for Public Opinion Research (DC-AAPOR) and the Washington Statistical Society 

(WSS) (January 2010) 

 Data Capture Technology Forum (March 2010) 
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 AAPOR Panel on Respondent Record Use (May 2010) 

 Data User Needs Forum (June 2010) 

 CE Methods Workshop (December 2010) 

 Consensus Expert Panel First Meeting (February 2011) 

 Household Survey Producers Workshop and Consensus Expert Panel Second Meeting 

(June 2011) 

 CE Redesign Options Workshop and Consensus Expert Panel Third Meeting (October 

2011)

 Consensus Expert Panel Fourth Meeting (January 2012) 

 Survey Methods Symposium (July 2012) 

 CNSTAT Report Workshop (scheduled for October 2012) 

Subsequent events have focused on the proposed redesign, as well as issues identified during past events 

and other survey methods topics of interest. 

The following significant reports and contracts were also completed or awarded during Stage 1: 

 Data Quality Definition Report (October 2009) 

 CPI Requirements Paper (June 2010) 

 Conference Team Report (August 2010) 

 CNSTAT Consensus Expert Panel contract awarded (September 2010) 

 CE Data Requirements Report (May 2011) 

 Independent Redesign Proposals II contract awarded (June 2012)1

 Gemini Technology Team Report (June 2012)2 

 Gemini Sampling Team I Report (September 2012)3

 Small-scale Redesign Project Report (September 2012)4

 

1 A contract with a vendor was awarded for the development and proposal of a CE Redesign given updated 

CE design decisions, cost estimates, and preliminary reconciled expenditure categories. Their first proofof-concept presentation will be in November 2012.

2 This team comprised of BLS and Census members reviewed the research literature to-date and 

recommended the most promising technologies for the CE Redesign Proposal. 

3 This team estimated sample sizes required for the CED and CEQ based on a preliminary list of reconciled 

expenditure categories. 

4 The Gemini Steering Team met during Winter and Spring of 2012 to discuss small-scale changes that 

could be made to CE. The goals of these changes were to reduce respondent burden by streamlining the 

interview, reduce costs, and to improve data quality (e.g., measurement error) to the extent possible without 

increasing burden or cost. A memo of suggested changes for 2015 was delivered and a memo for 

suggested changes for 2017 will be generated.
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 OPLC Requirements Team Report (expected October 2012)5

 Independent Redesign Proposals II proof-of-concept presentation (November 2012) 

The team that developed the CE Resign Proposal, the Gemini Design Team, was a joint BLS-Census team 

which kicked-off in July 2012 and submitted their proposal in July 2013, at which time it was also approved 

by BLS management. 

Stage 2 integrated research findings from Stage 1 into a coherent plan consisting of two major steps: 1) 

Assessing user impacts and 2) Finalizing the redesign roadmap for piloting, evaluating, and transitioning to 

the new design. The redesign roadmap was completed in September 2013, and a Data User Impact report 

was released in February 2014. 

Pilot testing the proposed redesign, conducting additional research on alternative designs, and 

implementing the approved redesign can be considered a 3rd stage of the redesign process. Stage 3 

includes work to develop, test, and implement the survey redesign using the redesign roadmap approved 

by senior management. More detail on current and upcoming projects that are included in stage 3 can be 

found in the Gemini Research Agenda (http://www.bls.gov/cex/gemini_web_report.pdf), which will be 

regularly updated. 

 

5 This team reconciled CE-CPI data requirements into one set of reconciled expenditure categories. 
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Redesign Topics 

Many different elements of survey methodology affect a survey redesign. Table 1 includes a list of those 

topics that were most critical for preliminary discussions for a redesigned CE, a description of each, and 

examples of the forums where the topic were discussed. Some topics, such as administrative records or 

other external data, have been researched and determined to be sufficiently infeasible that CE will not 

continue to investigate them. In the case of administrative records, this decision was made due to concerns 

about complexity from multiple data collection streams, resource constraints, quality of administrative data, 

respondent compliance, source compliance (e.g., store or third party aggregator), representativeness, and 

other risks due to loss of control over collection. Note that Table 1 is not meant to be a complete list of 

topics, nor is it a complete list of venues for discussion. 

More information about in-progress and planned BLS research projects to support the survey redesign can 

be found on the Gemini Project website at http://www.bls.gov/cex/geminimaterials.htm. Since these 

projects span a number of the survey methods topics, it made sense to list them separately rather than 

fitting them into this table. 

Table 1. Topics for Investigation and Further Research (listed alphabetically)

Topic Description Forum for discussion

Administrative 

records/external 

data

Some of the information that CE collects 

is collected in other sources. Using 

external data could reduce respondent 

burden and potentially improve data 

quality (depending on the quality of the 

external data). 

- Household Survey 

Producers Workshop (June

2011) 

- CE Redesign Options 

Workshop (October 2011)

Data user needs It is important to get input from data 

users to understand their uses of the 

data and to get suggestions for changes 

to the surveys.

- On an ongoing basis, keep 

users informed of the status 

of the project through 

meetings and 

presentations, including the 

expert panel

- Data User Needs Forum

(June 2010)

Mixed-mode 

designs

Offering more than one data collection 

mode (e.g., telephone or web) may 

increase response rates and reduce bias. 

BLS must determine how to design and 

implement a successful mixed-mode 

survey.

- Household Survey 

Producers Workshop (June 

2011) 

- CE Redesign Options 

Workshop (October 2011)
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Topic Description Forum for discussion

New technology BLS will examine technologies for data 

collection, such as PDAs, smart phones, 

or various types of scanning 

technologies, and determine their 

possible use and cost for CE.

- Data Capture Technology 

Forum (March 2010)

- Westat’s “Data Capture 

Technology” presentation at 

FedCASIC (March 2011)

- Household Survey 

Producers Workshop (June 

2011)

- CE Redesign Options 

Workshop (October 2011)

- Survey Methods 

Symposium (July 2012)

Proxy reporting Collecting data from all consumer unit 

members may result in better reporting. 

BLS will determine how best to collect 

data from all consumer unit members

without increasing unit nonresponse.

- Household Survey 

Producers Workshop (June 

2011)

- CE Redesign Options 

Workshop (October 2011)

Questionnaire 

design

The use of alternative designs for the CE 

survey may allow for more efficient data 

collection or the collection of higher 

quality data. BLS will determine how CE 

can incorporate different types of 

interview structures or technology-driven 

approaches into the data collection 

process.

- Survey Redesign Panel 

Discussion, sponsored by 

DC-AAPOR and WSS 

(January 2010)

- CE Methods Workshop

(December 2010)

Recall period A shorter recall period may result in 

better recall and therefore higher quality 

reporting. On the other hand, contacting 

respondents more often (such as

monthly) might lead respondents to stop 

reporting or to report fewer expenditures. 

- CE Methods Workshop

(December 2010)

Records and recall 

aids

Increased reliance or improved guidance 

on records, receipts, and recall aids, 

including electronic records, may result in 

better reporting. BLS will determine how 

these resources can be integrated 

effectively into the CE.

- AAPOR Panel on 

Respondent Record Use

(May 2010)
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Topic Description Forum for discussion

Required data 

elements and 

features in 

redesigned survey

A formal process to specify the data 

elements, both expenditure and 

nonexpenditure, and ancillary features, 

including timeliness and periodicity, 

necessary to satisfy the needs of the CPI, 

CE and DPINR programs. This will 

become a requirements document to guide 

design teams on the data the redesigned 

CE survey should obtain.

- OPLC Requirements for CE 

Team (October 2012)

Respondent burden An interview that is shorter or less 

burdensome cognitively could result in 

better reporting, higher retention rates,

and reduced bias in later interviews. 

Possible approaches might include 

increased use of screener questions or 

asking subsets of questions 

supplemented by global questions in 

place of the whole interview. 

- CE Methods Workshop

(December 2010)

Criteria for Success 

The success of the Gemini Project will be judged based on the accomplishment of the following criteria, 

listed in descending order of priority: 

1. There is a measurable reduction in measurement error. 

2. There is an overall increase in data quality, including a balanced evaluation of the mean 

squared error of the cost weights, and reduction of components of bias and variance 

attributable to specific sources of sampling or nonsampling error, such as unit nonresponse, 

wave nonresponse, or item nonresponse. Data quality criteria may also include other factors 

such as timeliness. Practical decisions on methodology and field operations will involve tradeoffs among cost and error factors for different components of bias and variance. Realistically, it 

is not expected that there will be uniform improvement in all components of error: some will 

decrease, and some will increase. 

3. The analytic value of CE data for researchers and policymakers is maintained or improved, both 

for microeconomic and macroeconomic data users. 
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To the extent possible, it is also important that the new design supports a greater operational flexibility to 

respond to changes in the interviewing environment, and that results from the success criteria are 

reasonably robust against future changes in societal and technological factors and variability in budgetary 

levels. 

Stakeholders 

The stakeholders for the Gemini Project include all groups involved in or concerned about the impact of 

survey design changes on the collection, processing, editing (including imputation and allocation), 

weighting, estimation, evaluation, quality, and use of CE data. These groups include: 

 

 BLS Associate Commissioner, Office of Prices and Living Conditions (OPLC) 

 BLS Division of Consumer Expenditure Information Systems (CEIS) 

 BLS Division of Consumer Expenditure Survey (DCE) 

 BLS Division of Consumer Prices and Price Indexes (CPI) 

 BLS Division of Price and Index Number Research (DPINR) 

 BLS Division of Price Statistical Methods, Branch of Consumer Expenditures (SMD) 

 Bureau of the Census (BoC) 

 Other Federal Agencies including the Bureau of Economic Analysis (BEA), the Internal 

Revenue Service (IRS), and the Department of Defense (DoD) 

 Other individual users of CE microdata and published estimates in the academic, Government, 

nonprofit, and commercial sectors. 
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Attachment 1. Gemini Project Timeline 

The current high level timeline is maintained on the Gemini website, accessible at 

http://www.bls.gov/cex/geminitimeline.pdf. 

Below is a list of past completed tasks for Stages 1 and 2 of the Gemini project.

2009

February Milestone - Gemini Project kick-off

March Milestone - Research Project Tracking System Team, Redesign Conference 

Team and Data Quality Team chartered

July Milestone - Expert Panel chartered

August Milestone - Expert Panel kickoff meeting

October Deliverable - Data Quality Definition report completed

December Deliverable - CE Methods Workshop issue papers completed 

2010

January Event - Survey Redesign Panel Discussion featuring representatives from 

five major Federal surveys 

March Event - Data Capture Technology Forum

May Event - AAPOR (American Association for Public Opinion Research) Panel on 

Respondent Record Use

June Event - Data User Needs Forum

August Deliverable - Data User Needs Team report completed 

August Deliverable - Conference Team report completed

November Deliverable - Statement on CE Data Priorities released

December Event - CE Methods Workshop 

December Deliverable - Research Project Tracking System report completed
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2011

June Event - Household Survey Producers Workshop

October Event - CE Redesign Options Workshop

2012

June Deliverable - Gemini Technology Team Report

July Event - CE Survey Methods Symposium

August Deliverable - CNSTAT Consensus Expert Panel pre-publication report

September Deliverable - Gemini Sampling Team I Final Report 

October Deliverable - Public release of the CNSTAT Consensus Expert Panel report

October Deliverable - OPLC Requirements Team Report

October Event - CNSTAT Consensus Expert Panel Report Workshop

Fall and Winter Milestone - Develop models for redesign

December Milestone - Presentation at Federal Economic Statistics Advisory Committee 

Meeting

2013

July Deliverable - Gemini Design Team proposal completed

July Milestone - Presentations of the Redesign Proposal to CE Management for 

review and approval

July Event - CE Survey Methods Symposium and public release of the 

design plan

July -December Deliverable - Detailed redesign roadmap & presentations for proposed 

redesign

2014

April Deliverable - User Impact Team report published