About CHIS

More than 20,000 California households — including adults, adolescents, and children — are interviewed each year, and several years of data can be combined to create an even larger sample.  

Interviews are conducted in six languages: English, Spanish, Chinese (Mandarin and Cantonese), Korean, Japanese, Vietnamese, and Tagalog. CHIS is especially known for its hard-to-find data on racial and ethnic subgroups and underserved communities.  

CHIS is a web and telephone survey conducted on a continuous basis, allowing the survey to generate timely one-year estimates. Participants in the survey are chosen at random and the sample is extensive enough to be statistically representative of California's diverse population. 

Beginning in 2019, CHIS switched from a sample of telephone numbers to a sample of addresses. Moving to an address-based sample improves the coverage of California households, allows for more modes of contact and data collection, and counteracts declining participation by telephone due to the rise of spam calls, robocalls, and call blocking.  

When CHIS contacts a household, one adult is randomly selected to participate in the survey. In addition, an adolescent (ages 12–17) and/or a child (ages 11 and under) may be randomly selected, depending on the household's composition. Selected participants can now complete the survey on the web or by telephone.

CHIS covers a broad range of health topics, including: access to and use of health care, health insurance, health status, health conditions (asthma, diabetes, cancer, etc.), health behaviors (smoking, alcohol use, diet, etc.), public program participation (Medi-Cal, food stamps, CalWorks, etc.), mental health, oral health, immigrant health, intimate partner violence, food, childcare and school, employment, income, discrimination, and much more. Many core questions are repeated in each survey in order to measure significant shifts over time.  

New questions are also added each survey year to address emerging concerns that are important for planning and policy development. Over the last few years, CHIS has added a series of questions on COVID-19, gun violence, housing, climate change, encounters with police, adverse childhood experiences, and much more.  

Topics can be viewed across a range of sociodemographic factors, including: race and ethnicity, age, gender, sexual orientation and gender identity, education, citizenship, language, veteran status, and more. 

To see a complete list of the health topics covered by CHIS, visit the Questionnaires and Survey Topics website.  

CHIS surveys are conducted in all 58 counties of California. CHIS may also conduct oversampling and small-area estimates of certain counties, such as Los Angeles and San Diego.  

Visit the Detailed Design website for a complete list of downloadable tables that show the number of people CHIS has interviewed for each county, as well as their race and ethnicity during recent data collection cycles.   

Would you like an oversample of your city or geographic area? Contact the CHIS team to learn more about expanded survey options.  

CHIS provides data at the state and county level, as well as more granular levels, including ZIP code, city, legislative district, and census tract. 

• Statewide information on the overall population including many racial and ethnic groups.  

• County-level information for most counties to aid with health planning, priority setting, and to compare health outcomes in numerous ways. 

• More granular information, including at the ZIP code, city, legislative district, and census tract-levels. 

The survey uses a scientific sampling methodology and extensive questionnaires to collect consistent information that accurately represents California's diverse populations and geographic areas. 

The California Health Interview Survey and UCLA Center for Health Policy Research are committed to putting data into the hands of all people through accessible online tools, publications, and trainings.  

CHIS data are released in the following formats: 

• AskCHIS: A free, online tool that enables you to produce customized health statistics at the state, county, region, or sub-county areas (for Los Angeles and San Diego counties). AskCHIS provides all CHIS data in an easy-to-use format. Several years of data can be combined to create larger samples.  

• AskCHIS Neighborhood Edition (NE): A free, online tool that enables you to generate, map, and export customized estimates of California cities, ZIP codes, legislative districts, and census tracts. AskCHIS NE provides data on select topics in an easy-to-use format. 

• CHIS COVID-19 Estimates Dashboards: This tool provides early CHIS estimates focused on Californians’ health status, behaviors, and experiences related to the COVID-19 pandemic. 

• Data Access Center (DAC): CHIS’ Data Access Center provides researchers with access to CHIS data that are not publicly available through an approval process.  

• Public Use Files (PUFs): The data files contain a full cycle of CHIS data, enabling researchers to customize and run their own data searches. The files are available in the following data formats: SAS and Stata.

• Publications: The UCLA Center for Health Policy Research, which conducts CHIS, produces various publications, including fact sheets, policy briefs, infographics, and reports using CHIS data.  

• Health Profiles: Easy-to-understand fact sheets and interactive dashboards containing key health statistics for the state, California counties, regions, Service Planning Areas (SPAs), and more.

Legislators, policymakers, local health departments, state agencies, health care providers, community organizations, advocacy groups, foundations, researchers, and many others use CHIS data to justify programs that fight health threats and aid policies that improve public health.  

Health care reform. Health insurance coverage. Chronic diseases. Health inequities. On a broad range of important health topics, CHIS data are invaluable for policymakers at the local, state, and national levels to make informed decisions, as well as compelling arguments. CHIS data have been used to ground dozens of important health initiatives, including: 

California Health Care Reform: 

• CHIS is one of the data sources for the California Simulation of Insurance Markets (CalSIM)​, a microsimulation model created by the UC Berkeley Labor Center and the UCLA Center for Health Policy Research. To date, CalSIM has helped California’s state and local health officials, Covered California, the state's Health Benefit Exchange, medical providers, community representatives, insurance companies, and others to understand the enrollment of Californians in an expanded Medi-Cal program and in Covered California. CHIS has also helped project how the “individual mandate” might impact coverage, as well as who will be left out of new health care reform efforts.  

• The California Health Benefits Review Program (CHBRP), which provides the California State Legislature with independent analysis of the medical, financial, and public health impacts of proposed health insurance benefit mandates and repeals, uses CHIS data for analysis or background for various bills each year. 

• Two Center publications that used CHIS data were cited in an amicus brief filed before the U.S. Supreme Court by The California Endowment to support the “individual mandate,” which the court upheld. One publication found that without the mandate, the number of newly insured Californians would be 1.04 million lower in 2019 than with the mandate. Another publication estimated that up to two-thirds of California's uninsured might get health insurance coverage under health care reform.  

• CHIS has also been instrumental to earlier health care reform efforts, including reform proposals developed by both former California Governor Schwarzenegger's office and Democratic legislators. Advocacy groups on all sides of the issue also relied on CHIS data to inform their positions and craft their arguments. 

Food 4 All: 
Nourish California and the California Immigrant Policy Center launched the Food4All campaign in 2021, co-sponsoring Senate Bill (SB) 464 with Senator Melissa Hurtado, which would modernize the California Food Assistance Program (CFAP) and make the program accessible to all Californians regardless of their citizenship status. In partnership with UCLA CHPR and using CHIS data, the Food4All Campaign released a report that revealed that nearly half (45%) of undocumented Californians are currently experiencing food insecurity, including 64% of children. The data and report were used in advocacy efforts and by policymakers and legislators.  

In June 2022, California Governor Gavin Newsom and the California Legislature finalized the 2022–2023 State Budget, which includes funding for Food4All to remove exclusions to CFAP/CalFresh for Californians 55 and older, regardless of citizenship status. 

Public Charge 
U.S. immigration officials use the term “public charge” to describe people applying for a green card who are deemed likely to become primarily dependent on the government to meet their basic needs.  

• In 2018, the U.S. Department of Homeland Security proposed changing the so-called “public charge” rule, which would broaden the definition of public charge to include immigrants who use one or more government programs such as Medicaid, SNAP (formerly known as food stamps), and housing assistance, and add specific requirements to the public charge test for income, health, age, and even English proficiency. The proposal would drastically expand the grounds on which an immigrant could be denied legal permanent residency or admission to the United States. UCLA CHPR researchers conducted a rapid analysis to understand the potential impact on health, the health workforce, and the economy. The research was cited hundreds of times by organizations and individuals providing public comments on the proposed rules.  

• In 2020, the U.S. Court of Appeals for the Ninth District: City and County of San Francisco vs. U.S. Citizenship and Immigration Services cited CHIS data as evidence to oppose public charge with data on the number of people who would disenroll in Medicaid and other public services.  

• In 2022, Public Charge Ground of Inadmissibility, a proposed rule by the U.S. Department of Homeland Security cited a UCLA CHPR policy brief, “One in 4 Low-Income Immigrant Adults in California Avoided Public Programs, Likely Worsening Food Insecurity and Access to Health Care.” 

CHIS is conducted by the UCLA Center for Health Policy Research, in collaboration with the California Department of Public Health and the Department of Health Care Services.  

CHIS Principal Investigator Ninez A. Ponce, PhD, MPP, is a noted authority on health data as well as on health and health care access issues among marginalized populations.  

CHIS Director Todd Hughes is a leader in survey research with more than 25 years of experience managing population-representative household surveys.  

CHIS is also supported by an advisory board comprising prominent leaders in public health and health care, and led by California Health and Human Services Director Dr. Mark Ghaly. 

CHIS users and funders share how CHIS has helped them. 

“It becomes like the Bible. It came out of UCLA; it came out of CHIS — you know it’s reliable.”  
Richard Figueroa 
Deputy Cabinet Secretary, Office of the Governor  
Former Acting Director, California Department of Health Care Services 
 

“The California Health Interview Survey is one of its kind in the nation and the largest comprehensive opportunity to get a look at cross-cutting information. I am proud to be the Agency Secretary that supports the two departments that are major financial contributors to this survey.”  
Dr. Mark Ghaly 
Secretary, California Health and Human Services  
 

“CHIS really provided the backbone for California’s estimates of the number of uninsured and the nature of our uninsured population. We were very fortunate to have CHIS and have a very robust and meaningful database to help us understand, not only how many Californians are uninsured, but the nature of those individuals — in terms of their income, in terms of their age, in terms of their immigration status, and so forth. In California, we were very fortunate. We had a lot of arguments, a lot of problems with the policy, but we didn’t have arguments about the numbers. And in large part that is because of CHIS, and CHIS being viewed as a very reliable and objective and meaningful source of information to inform policy and debate policy judgments.” 
Kim Belshé 
Former Executive Director, First 5 LA 
Former Secretary, California Health and Human Services Agency  
 

“One model is the California Health Interview Survey (CHIS), launched in 2001 and conducted by UCLA’s Center for Health Policy Research. It ‘is the only population- based data that I trust. Anything else I don’t bother reading.”  
Tung Nguyen 
Professor of Medicine, University of California San Francisco 
(featured on Bloomberg.com) 
 

“CHIS is an incredible tool for policymakers — both the talented Center’s researchers and students comprise an invaluable brain trust for public health. Part of the Center’s mission is to train the next generation of health policy researchers and advocates. Hundreds of public health professionals doing essential work on the most pressing health issues of our time got their start at the UCLA Center for Health Policy Research.” 
Diana Bontá, PhD 
President and Chief Executive Officer 
The Bontá Group  
 

"State policymakers regularly rely on the integrity of CHIS data. We have hard decisions to make and now, more than ever, this data is essential to the well-being of the people of California." 
Diana Dooley 
Former Secretary, California Health and Human Services Agency 
 

“State and local policymakers should require the collection and reporting of disaggregated sociodemographic data, including race, ethnicity, language, sexual orientation, gender identity, and disability status, especially at the neighborhood level. Where possible, agencies should model their approaches off of existing best practices for disaggregated data collection and reporting, such as the approach used by the California Health Interview Survey.” 
California Pan-Ethnic Health Network


"I'm a huge fan of CHIS. As Director, I heavily rely on its data, in terms of the decisions I make, and the decisions that our state's Assemblymembers, Senators and Governor make. It's hard to imagine what it'd be like to apply for funding and make decisions without CHIS." 
Ronald W. Chapman 
Former Director, California Department of Public Health 
 

"CHIS data is remarkably important to our advocacy efforts and our work with the media. It gives us a baseline of the state's problems so that we can tell if we're making progress." 
Anthony Wright 
Executive Director, Health Access 


"We have used CHIS data to really understand the barriers that communities of colors face when getting the care that they need." 
Ellen Wu 
Executive Director, Urban Habitat                                 
Former Executive Director, California Pan-Ethnic Health Network 


"CHIS data adds credibility to all the work that we do." 
Pamela Lane 
Vice President, Health Informatics at California Hospital Association 


“CHIS has been an important resource for CHBRP for many years, particularly since the Affordable Care Act was implemented in California. In order to project potential impacts of proposed legislation in California, CHBRP develops a comprehensive estimate of sources of health insurance for all Californians. This baseline population modeling relies heavily on CHIS. In addition, CHIS informed all 19 legislative analyses completed by CHBRP in 2021 either directly or indirectly.” 
Garen Corbett  
Director, California Health Benefits Review Program (CHBRP)