SIPP is a complex longitudinal survey that is continually addressing sample attrition and nonresponse bias. The 2020 SIPP faced additional data collection complications because of the COVID-19 pandemic. Due to government restrictions, mandated stay-at-home orders, and health and safety concerns for both Census interviewers and sampled households, the 2020 SIPP switched to telephone-only interviewing on March 19, 2020. Telephone-only interviewing continued through June 30, the end of the 2020 data collection period. Because SIPP relies on in-person interviews to collect the best data from our sampled households, telephone-only interviewing significantly disrupted our ability to reach and follow-up with respondents – especially those in their initial sample year. This led to lower-than-average unit response rates nationally.

To monitor and improve data quality during collection, SIPP’s geographic Primary Sampling Unit (PSU) are reviewed to identify areas that have insufficient representation (coverage). Adaptive design case prioritization and active field management are used to achieve both an increase in representativeness and ensure a minimum level of coverage.

Even with these data collection mitigations, the low unit response rate in 2020 SIPP led to item response rates and coverage ratios that do not meet the Census Bureau’s Statistical Quality Standards. The SIPP program creates weights designed to adjust for nonresponse and to control weighted counts to independent population estimates by age, sex, race, and Hispanic origin. However, the magnitude of the increase in (and differential nature of) nonresponse during 2020 data collection likely reduces their efficacy. As a result, data users should use caution when creating estimates using 2020 SIPP data, including the longitudinal 2018 Panel subsample.

Additional information on nonresponse bias for data collected in calendar year 2020 will be available in the upcoming Nonresponse Bias Report for Calendar Year 2020 of the Survey of Income and Program Participation. More details about 2020 SIPP’s unit response rate, sample attrition, and item response rates for SIPP’s key estimates are forthcoming.