SIPP is a complex longitudinal survey that is continually addressing sample attrition and nonresponse bias. SIPP faced additional data collection complications because of the 2019 lapse in federal funding that stopped operations for 35 days during a critical hiring, onboarding, and training period. Data collection for 2019 SIPP began with insufficient staff and significantly delayed training of field interviewers. Some geographies remained understaffed throughout data collection. This staffing deficit occurred in conjunction with lower-than-average unit response rates nationally. To maintain cross-sectional data quality, SIPP implemented overlapping samples beginning in 2019, adding new cases each year; however, it was necessary to deprioritize the 2019 Wave 1 cases during collection to focus effort on maintaining the 2018 Wave 2 cases for longitudinal purposes with the expectation that a new sample would be added in 2020.

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 2019 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 2019 data collection likely reduces their efficacy. As a result, data users should use caution when creating estimates using 2019 SIPP data, including the longitudinal 2018 Panel subsample.

Additional information on nonresponse bias for data collected in calendar year 2019 will be available in the upcoming Nonresponse Bias Report for Calendar Year 2019 of the Survey of Income and Program Participation. More details about 2019 SIPP’s unit response rate, sample attrition, and item response rates for SIPP’s key estimates are forthcoming.