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This survey was designed and analyzed by public opinion researchers at the Kaiser Family Foundation (KFF). Interviews were conducted by telephone from September 13th-24th and October 5th-10th, 2017 among a nationally representative random digit dial telephone sample of 2,505 adult U.S. residents. This includes interviews conducted as part of the September and October Kaiser Health Tracking Polls, as well as an oversample of respondents who purchase their own insurance (Non-Group Enrollees). Computer-assisted telephone interviews conducted by landline (867) and cell phone (1,638 including 1,041 who had no landline telephone) were carried out in English and Spanish by SSRS. For the landline sample, respondents were selected by asking for the youngest adult male or female currently at home based on a random rotation. If no one of that gender was available, interviewers asked to speak with the youngest adult of the opposite gender. For the cell phone sample, interviews were conducted with the adult who answered the phone. KFF paid for all costs associated with the survey.

Respondents were considered Non-Group Enrollees if they were between the ages of 18-64 and their main source of healthcare coverage is health insurance that they purchase themselves (excluding small business owners whose self-purchased insurance covers non-related employees). To efficiently obtain a sufficiently large sample of Non-Group Enrollees, given their overall low incidence in the general adult population, the sample included a subsample of respondents who had previously completed interviews on the SSRS Omnibus poll, and indicated that they met the specifications of Non-Group Enrollees (n=111). All RDD landline and cell phone samples were generated by Marketing Systems Group (MSG). The SSRS Omnibus poll involves a similar overlapping frame design.

A multi-stage weighting process was applied to ensure an accurate representation of the national population overall, and of non-group enrollees in particular. The first stage of weighting involved corrections for sample design, including accounting for the likelihood of non-response for the re-contact sample, number of eligible household members for those reached via landline, and a correction to account for the fact that respondents with both a landline and cell phone have a higher probability of selection.

In the second weighting stage, demographic adjustments were applied to account for systematic non-response along known population parameters. First, interviews conducted as part of the Health Tracking Poll (excluding the Non-Group Enrollee oversample) were weighted to match estimates for the national population using data from the Census Bureau’s 2015 American Community Survey (ACS) on sex, age, education, race, Hispanic origin, and region along with data from the 2010 Census on population density and current patterns of telephone use from the July-December 2016 National Health Interview Survey. This weighted sample was used to estimate the population share of Non-Group Enrollees, as defined for this study. The combined sample of Non-Group Enrollees (from both the Health Tracking Poll and the oversample) was then weighted separately, and scaled down to the proportion of Non-Group Enrollees in the weighted general population sample.

No reliable administrative data were available for creating demographic weighting parameters for Non-Group Enrollees, since the most recent Census figures could not account for the changing demographics of this group, specifically as they are defined in this study. Therefore, demographic benchmarks were derived by compiling a sample of all respondents ages 18-64 interviewed on the SSRS Omnibus survey between March 1 and August 27, 2017 (N=24,818) and weighting this sample to match the national 18-64 year-old population based on the 2017 U.S. Census Current Population Survey March Supplement parameters for age, gender, education, race/ethnicity, region, population density, and marital status, as well phone use based on the most recent estimates from the National Health Interview Survey (NHIS). This weighted sample was then filtered to include respondents meeting the definition of Non-Group Enrollee (N=2,245), and the demographics of this group were used as post-stratification weighting parameters for the combined Non-Group enrollee sample. Finally, weighted samples were combined and a final adjustment was applied to account for the over-representation of Non-Group Enrollees in the sample.

The margin of sampling error including the design effect for the full sample is plus or minus 2 percentage points. Numbers of respondents and margins of sampling error for key subgroups are shown in the table below. For results based on other subgroups, the margin of sampling error may be higher. Sample sizes and margins of sampling error for other subgroups are available by request. Note that sampling error is only one of many potential sources of error in this or any other public opinion poll. Kaiser Family Foundation public opinion and survey research is a charter member of the Transparency Initiative of the American Association for Public Opinion Research.

Group N (unweighted) M.O.S.E.
Total 2,505 ±2 percentage points
Non-Group Enrollees ages 18-64 295 ±7 percentage points
Age 18-64 with Employer Insurance 935 ±4 percentage points
Uninsured ages 18-64 206 ±7 percentage points
Marketplace Enrollees ages 18-64 195 ±9 percentage points

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Filling the need for trusted information on national health issues, the Kaiser Family Foundation is a nonprofit organization based in Menlo Park, California.