Guidance for Pooling Multiple Years of NHIS Data

By Julia A. Rivera Drew

Introduction

Depending on their research question, analysts will commonly pool multiple years of the National Health Interview Survey (NHIS) data together in order to increase sample sizes of particular subpopulations of interest, such as bisexual adults, immigrants, or pregnant women. The complex design of the NHIS, however, requires analysts to take additional steps to correctly construct and analyze pooled NHIS datasets. Moreover, planned changes to the NHIS design implemented in 2019, as well as changes made in response to the COVID-19 pandemic, require additional special handling to correctly analyze datasets combining multiple years of NHIS data. The objectives of this blog post are to: (1) share tips to correctly construct and analyze pooled NHIS datasets and (2) identify resources for more information.

Tips to Correctly Construct and Analyze Pooled NHIS Datasets

1. Create a pooled sampling weight to use with your pooled dataset.

In general, when pooling multiple years of NHIS data together, you will need to create a new sampling weight to use with the pooled sample. To create this new sampling weight, divide the appropriate sampling weight by the number of years within each distinct sample design period. For example, if one wished to estimate the number of children living in families with low or very low food security (FSSTAT) using pooled 2020-2021 NHIS data (e.g., similar to this report), one would need to create a new sampling weight by dividing the sampling weight identified under the “weights” tab for FSSTAT, SAMPWEIGHT, by the number of years pooled together from the same sampling design period (in this case, two). The sum of the pooled weights would then represent the average annual population size for the pooled time period, rather than the total cumulative population size for the pooled time period. For any given combination of variables, refer to information under the “weights” tab for the variables included in your analysis to help select the appropriate sampling weight. The distinct NHIS sample design periods are 1963-1974, 1975-1984, 1985-1994, 1995-2005, 2006-2015, 2016-2018, and 2019-present.

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Using the MEPS-HC to Study Change in Adult Mental Health

By Julia A. Rivera Drew and Natalie Del Ponte

The Medical Expenditure Panel Survey-Household Component, or MEPS-HC, data are an invaluable resource for studying short-term trajectories in health, including adult mental health. An integrated series of the MEPS-HC data is available at IPUMS MEPS. Collected on the Self-Administered Questionnaire and, starting in 2019, the Preventive Self-Administered Questionnaire, the MEPS-HC includes two validated adult mental health scales. The Kessler Psychological Distress Scale (K6) and the two-item Patient Health Questionnaire depression screener (PHQ-2) are asked twice per panel, during interview rounds 2 and 4 (see Table 1). There are also two validated scales measuring health-related quality of life (HRQOL) that capture several interrelated health domains, including mental health. These include the Short Form-12 (SF-12) in 2000-2016 and the Veterans RAND-12 (VR-12) starting in 2017 (see Table 2 for VR-12 measures). For more information on the SF-12, see the section on SF-12 scoring on MCS and for more information on the VR-12, see ADDAYA.

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An Age-Based Approach to Disability

By Solvejg Wastvedt and Yash Singh

Disability is dynamic: it evolves over time and interacts with environmental and societal factors. Due to the complex nature of disability, researchers conceptualize and measure disability differently depending on their research question and available data. For instance, an identical condition might evolve differently for a child facing food insecurity compared to one that has stable access to food. Similarly, a physical limitation for a worker in New York City may have a vastly different impact compared to a similar worker in rural Iowa. Disability can be viewed as the relational concept between individuals with physical or mental impairment and the environment.1 2 This complexity makes measuring disability a challenging task. The following post aims to help researchers understand and use disability measurements available in IPUMS data collections.

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IPUMS Announces 2020 Research Award Recipients

IPUMS research awardsIPUMS is excited to announce the winners of its annual IPUMS Research Awards. These awards honor the best-published research and nominated graduate student papers from 2020 that used IPUMS data to advance or deepen our understanding of social and demographic processes.

IPUMS, developed by and housed at the University of Minnesota, is the world’s largest individual-level population database, providing harmonized data on people in the U.S. and around the world to researchers at no cost.

There are six award categories, and each is tied to the following IPUMS projects:

  • IPUMS USA, providing data from the U.S. decennial censuses, the American Community Survey, and IPUMS CPS from 1850 to the present.
  • IPUMS International, providing harmonized data contributed by more than 100 international statistical office partners; it currently includes information on 500 million people in more than 200 censuses from around the world, from 1960 forward.
  • IPUMS Health Surveys, which makes available the U.S. National Health Interview Survey (NHIS) and the Medical Expenditure Panel Survey (MEPS).
  • IPUMS Spatial, covering IPUMS NHGIS and IPUMS Terra. NHGIS includes GIS boundary files from 1790 to the present; Terra provides data on population and the environment from 1960 to the present.
  • IPUMS Global Health: providing harmonized data from the Demographic and Health Surveys and the Performance Monitoring and Accountability surveys, for low and middle-income countries from the 1980s to the present.
  • IPUMS Time Use, providing time diary data from the U.S. and around the world from 1965 to the present.

Over 2,500 publications based on IPUMS data appeared in journals, magazines, and newspapers worldwide last year. From these publications and from nominated graduate student papers, the award committees selected the 2020 honorees.

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How has COVID-19 affected 2020 data collection efforts?

By Julia A. Rivera Drew, Sarah M. Flood, Renae Rodgers

IPUMS integrates data from several major US surveys that collect data throughout the year. Below, we discuss how COVID-19 has affected how US statistical agencies have collected these survey data in 2020.

Current Population Survey (CPS)

The Bureau of Labor Statistics (BLS) and the Census Bureau have continued to collect data on a monthly basis during the COVID-19 pandemic, implementing some procedural modifications to protect the safety of respondents and Census Bureau employees and adding a short supplement to capture the effects of the pandemic on work in the United States.

Changes to Interviewing Procedures

Current Population Survey (CPS) data collection for March had already begun when the Census Bureau suspended in-person data collection on March 20th, 2020. Two call centers that assist with CPS data collection also closed down at this time. However, data collection continued exclusively by phone through June of 2020. In July, in-person interviews began in some areas of the country and the call centers that had been closed in March re-opened. In-person interviews were resumed in all areas of the country in September 2020 and data collection has returned to a normal routine. More information on how alternative data collection procedures affected response rates, attrition, and employment data is available on the IPUMS CPS website.

Additional COVID-related content

The COVID-19 outbreak prompted the BLS to add five questions to the monthly CPS survey about work in the time of COVID-19. These questions were first asked in May. Though the question about foregoing medical care due to the pandemic was dropped from the survey after October of 2020, all other questions will remain in the survey until further notice. Researchers may preview the questions or access the COVID-specific variables via IPUMS CPS.

IPUMS CPS will continue to update our documentation on the effects of the pandemic on CPS data collection and to make new data available as quickly as possible. Follow @ipums on Twitter for the latest updates.

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Overview of NHIS Data Collection, 1997-2018

By Julia A. Rivera Drew, Kari C.W. Williams, and Natalie Del Ponte

The IPUMS NHIS project offers integrated versions of the National Health Interview Survey (NHIS) data, the leading source of nationally representative information on the health of the U.S. population. The National Center for Health Statistics (NCHS) collects the NHIS data through face-to-face interviews covering information about health, health insurance coverage, health care utilization, socioeconomic characteristics, and demographics of all household members. It is representative of the civilian, non-institutionalized U.S. population with annual samples ranging between 30,000-50,000 households and 75,000-100,000 people. NCHS has collected the NHIS annually since 1957 (with digital copies of the data available going back to 1963), making it the longest running annual survey of health in the world.

Periodically, aspects of data collection – such as the sampling frame, oversampled populations, or questionnaire content – change to better capture changes in the most pressing health concerns of Americans or changes in the demographic makeup of ­­Americans and where they reside within the U.S. Most of these changes are modest, reflecting changes in U.S. population composition and distribution detected in the most recent decennial census. However, 2019 heralded the largest change in NHIS data collection since 1997. In fall 2020, the NCHS will release the 2019 public use data files, the first data collected under the newly redesigned NHIS. The upcoming release of the 2019 data warrants a look back at how NCHS collected the NHIS data over the 1997-2018 period.

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Updated variables in IPUMS CPS and IHIS ease discovery and research of same-sex and cohabiting couples

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IPUMS has updated the family interrelationship variables in IPUMS CPS and the Integrated Health Interview Series (IHIS) to include same-sex and cohabiting couples. The updated variables dramatically reduce research barriers for those interested in this family and household context.

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