Where are California's Uninsured Now? Wave 2 of the Kaiser Family Foundation California Longitudinal Panel Survey

This is the second in a series of surveys by the Kaiser Family Foundation (KFF) tracking the views and experiences of a group of Californians who were uninsured in the summer of 2013, prior to implementation of the ACA’s insurance market reforms and coverage expansions through Covered California and Medi-Cal. Future surveys will continue to track this group’s experiences over the course of the next year and a half. The first survey (Wave 1) was conducted from July 11-August 29, 2013, with a randomly selected group of individuals who were uninsured at the time of the interview and was paid for entirely by KFF. The current survey (Wave 2) was conducted from April 1-June 15, 2014, with the same longitudinal panel of respondents, whether they obtained coverage or remained uninsured. Both surveys were designed and analyzed by researchers at KFF. Social Science Research Solutions collaborated with KFF researchers on sample design, weighting, and supervised fieldwork. Fieldwork costs associated with Wave 2 of the survey were paid for by The California Endowment.

The Wave 1 survey was conducted among a representative random sample of 2,001 adults ages 19-64 living in California who reported having been without health insurance for at least two months at the time of the interview1 (note: persons without a telephone could not be included in the random selection process). Computer-assisted telephone interviews conducted by landline (990) and cell phone (1,011, including 660 who had no landline telephone) were carried out in English and Spanish by SSRS. To increase efficiency in reaching this low-incidence, hard-to-reach group, both the landline and cell phone sampling frames oversampled areas with a lower-income population (since being uninsured is negatively correlated with income). The landline sample frame also oversampled households whose phone numbers were matched with directory listings indicating the presence of at least one person age 19-64 and a household income of less than $25,000. Additionally, 230 interviews (130 landline, 100 cell phone) were conducted with respondents who previously completed recent national SSRS omnibus surveys of the general public and indicated they were ages 19-64 and uninsured. These previous surveys were conducted with nationally representative, random-digit-dial landline and cell phone samples.

The current survey, Wave 2, also consisted of computer-assisted telephone interviews conducted by landline (623) and cell phone (545, including 327 who had no landline phone) in English and Spanish. Screening for Wave 2 involved verifying that the respondent had participated in Wave 1. Multiple attempts were made to reach every respondent from Wave 1 and encourage participation in Wave 2. Efforts included multiple dialing at various times of day and throughout the week, mailings and emails to those who provided such contact information, repeated dialing of non-working numbers, and attempts to find alternative phone numbers for non-working numbers.

In order to re-connect with respondents who may be more willing to complete the survey online, an abbreviated web version was introduced on May 14. The online questionnaire was offered in English and Spanish and was limited to key questions about insurance status, type of coverage, and reasons for obtaining coverage or remaining uninsured. A total of 51 respondents completed the online version of the survey.

A multi-stage weighting design was applied to ensure accurate representation of California’s nonelderly adult uninsured population prior to the ACA’s coverage expansions. The weighting process for Wave 2 involved corrections for sample design, as well as sample weighting to match the weighted Wave 2 sample to Wave 1 responses along demographic characteristics. As it did for Wave 1, the Wave 2 base weight accounted for the oversamples used in the sample design, as well as the likelihood of non-response for the sample from earlier omnibus surveys, number of eligible household members for the landline sample, and a correction to account for the fact that respondents with both a landline and cell phone have a higher probability of selection. Demographic weighting parameters for Wave 2 were based on Wave 1 weighted demographics, which were adjusted for age, education, race/ethnicity, nativity (for Hispanics only), Hispanics by gender, presence of own child in household, marital status, California region, poverty level, and phone usage. For more information on weighting and data sources, see the Wave 1 methodology. All differences referred to in the report are statistically significant. Statistical tests of significance account for the effect of weighting, and, for trend analysis, testing takes into account the survey’s panel design.

A unique consideration for surveys with a longitudinal panel design is whether those who participate in subsequent waves of the survey differ from those who refuse to participate again or are unable to be recontacted. Sixty-one percent of Wave 1 respondents completed the Wave 2 survey, and while there are some differences in the unweighted demographics of those who completed Wave 2 and the full Wave 1 sample, these differences are corrected for by weighting. As shown in the table below the total weighted distributions are similar for Wave 1 and Wave 2 for age, gender, race/ethnicity, self-reported health status, disability status, party identification, education and income. See the Wave 2 Attrition Appendix for more information on attrition.

Unweighted Weighted
Percentage Point Wave
Percentage Point
Difference (W1 – W2) Difference (W1 – W2)
Male 48% 44% 4 54% 53% 1
Female 52 56 -4 46 47 -1
White 27 32 -5 26 27 -1
Black 7 8 -1 5 6 -1
Hispanic 58 52 6 56 55 1
Other Race 8 7 1 12 12 0
18 to 29 23 18 5 33 32 1
30 to 39 21 21 0 24 24 0
40 to 49 22 22 0 21 21 0
50 to 64 35 39 -4 22 24 -2
HS or less 57 53 4 58 57 1
Some college 28 31 -3 29 30 -1
College Grad+ 15 16 -1 12 13 -1
Phone status
Landline 49 54 -5 42 44 -2
Cell 51 46 5 58 56 2
Marital status
Married 33 32 1 37 37 0
Not Married 67 68 -1 62 63 -1
Family income
<138% FPL 60 59 1 52 53 -1
138%-400% FPL 30 32 -2 36 35 1
400%+ 5 5 0 7 7 0
Language of interview
English 63 68 -5 65 67 -2
Spanish 37 32 5 35 33 2
Resident status
Citizen/legal immigrant 79 82 -3 78 79 -1
Undocumented immigrant 20 16 4 21 19 2
Party identification
Republican 11 12 -1 11 12 -1
Democrat 35 36 -1 32 31 1
Independent 35 34 1 37 38 -1
Other 9 8 1 9 9 0

Another consideration for panel surveys is the potential for “sensitization effects,” that is, what effect returning to the same people about the same topics has on their experiences or views. For example, after taking the baseline survey that covered many aspects of the coverage expansions under the ACA, were people more likely to seek out information about health insurance and enroll than they would have been otherwise? While there is no direct way to measure this effect on this survey, other analyses have found that these effects are minimal and short-lived2 and we do not believe they would have had a substantial impact on results presented here, particularly given all the other media coverage, advertising, and outreach targeted at this population during the fall and winter of 2013 and 2014.

The margin of sampling error including the design effect for the full sample is plus or minus 4 percentage points. For the newly insured, it is plus or minus 5 percentage points and for the remaining uninsured it is plus or minus 7 percentage points. Numbers of respondents and margin of sampling error for key subgroups are shown in the table below.

Group N MOSE

Total Wave 2

1,219 +/- 4 percentage points

Newly insured

740 +/- 5 percentage points

Newly insured by non-group plan


+/- 11 percentage points

Newly insured through Covered California


+/- 13 percentage points

Newly insured by Medi-Cal


+/- 8 percentage points

Newly insured through an employer


+/- 12 percentage points

Newly insured Hispanics


+/- 8 percentage points
Remaining uninsured


+/- 7 percentage points
Remaining uninsured Hispanics


+/- 8 percentage points
Remaining uninsured undocumented immigrants


+/- 12 percentage points

For results based on other subgroups, the margin of sampling error may be higher. Sample sizes and margin of sampling errors 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.

Some demographic measures referred to in the report were only asked during the baseline survey, such as questions about educational attainment, debilitating chronic condition, length of time uninsured, resident status, and race/ethnicity. For more information on the first wave of the Kaiser Family Foundation California Longitudinal Panel Survey visit, https://www.kff.org/health-reform/report/californias-uninsured-on-the-eve-of-aca-open-enrollment/.

About The Terms Used In This Report

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