U.S. Census and American Community Survey microdata from 1850 to the present. Learn More about the IPUMS USA project
Current Population Survey microdata including basic monthly surveys and supplements from 1962 to the present. Learn More about the IPUMS CPS project
World's largest collection of census microdata covering over 100 countries, contemporary and historical. Learn More about the IPUMS International Project
Tabular U.S. Census data and GIS boundary files from 1790 to the present. Learn More about the IPUMS NHGIS Project
Tabular and GIS data from population, housing, and agricultural censuses around the world. Learn More about the IPUMS IHGIS Project
Historical and contemporary time use data from 1930 to the present. Learn More about the IPUMS Time Use Projects
Historical and contemporary U.S. health survey data from Visit the IPUMS NHIS site (1963-present) and Visit the IPUMS MEPS site (1996-present). Learn More about the IPUMS Health Surveys Projects
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.