Difference In Uninsurance Rates Between Full- And Part-Time Workers Declined In 2014

In 2017 nineteen million adults held part-time jobs in the United States.¹ Most employers do not offer health insurance benefits to part-time workers, placing coverage out of reach because of lower wages² and the high cost of nongroup coverage—especially for those whose part-time jobs are their sole source of income. Part-time work has increasingly become an involuntary employment status, especially in recent years.³ Consequently, insurance disparities between part- and full-time workers are critical to evaluate and monitor.

We examined nationally representative data for the period 2010–15 from the Medical Expenditure Panel Survey–Household Component (MEPS-HC) to understand whether work hours–related insurance gaps changed after the 2014 implementation of the main coverage reforms of the Affordable Care Act (ACA). We found that uninsurance rates decreased by 12–13 percentage points for part-time workers and by nearly 6 percentage points for full-time workers between 2010–13 and 2015 (exhibit 1). (We show results for 2015 to illustrate the full effects of the ACA’s expansion of eligibility for Medicaid to account for lagged enrollment effects.) Part-time workers in Medicaid expansion states gained coverage mainly through that public insurance program, while part-time workers in nonexpansion states gained coverage primarily from Marketplace plans. To our knowledge, our study is the first to evaluate changes in health insurance status by work hours and state Medicaid expansion status.

SOURCE Authors’ analysis of data for 2010–15 from the Medical Expenditure Panel Survey–Household Component. NOTES Changes shown are from 2010–13 to 2015. The exhibit shows linear probability estimates using sample weights. The population is wage earners ages 27–64. Full time and part time are defined as working an average of thirty or more hours a week and an average of less than thirty hours, respectively. Employer-sponsored insurance includes coverage for the worker and dependents. Significance refers to differences over time except as indicated. ^aDifference between full- and part-time workers is significant ($p<0.05$). ^bDifference between expansion and nonexpansion states is significant ($p<0.05$). *$p<0.10$ **$p<0.05$ ***$p<0.01$ ****$p<0.001$

The ACA includes many provisions that could have had differential impacts on workers, by both work hours and state Medicaid expansion status. For example, the mandate that medium-size and large employers offer health insurance to employees who work thirty or more hours per week or pay a penalty was targeted directly at full-time workers. In addition, workers with incomes below 138 percent of the federal poverty level were eligible for Medicaid in states that expanded eligibility in 2014. Finally, workers were eligible for Marketplace insurance subsidies based on their family income and offers of affordable employer-sponsored insurance, regardless of their state’s Medicaid expansion status.

Study Data And Methods

Data And Sample

We used individual-level data for 2010–15 from MEPS-HC. MEPS is the only nationally representative household survey of the US noninstitutionalized population that measured health insurance coverage status consistently during our study period and collected information on hours worked for current main jobs, among other detailed individual characteristics (see the online appendix).⁴

Our study sample included wage earners ages 27–64. We excluded young adults ages 18–26 because of the ACA’s dependent coverage provision. We also excluded self-employed workers. People who work fewer than thirty hours per week on average are defined as part-time workers, and those who average thirty or more hours per week are defined as full-time workers. Medicaid expansion state status is defined as whether or not the state of residence had expanded Medicaid by 2014 (see the appendix for sensitivity analyses using alternative definitions).⁴ In our analysis we defined 2010–13 as the pre-ACA implementation period, and we examined the ACA’s effects in 2014 and 2015 separately to account for lagged insurance enrollment.

Our main outcomes of interest were employer-sponsored insurance (as either the policyholder or a dependent), other private coverage, Medicaid, and uninsurance. “Other private coverage” is any private insurance unrelated to an employer offer; it includes insurance coverage that people purchased in the nongroup market or through the ACA Marketplaces. We also examined the likelihood of having eligibility for employer-sponsored insurance (from either one’s own or a spouse’s current main job) and the probability of taking up such coverage, conditional on being eligible.

Analytic Strategy

Our main findings were estimated with interrupted time-series models that controlled for a set of demographic and social characteristics, a linear year trend, and year and state fixed effects (see the appendix for full results).⁴ A linear time trend captures changes in macroeconomic conditions at the national level because the unemployment rate decreased linearly during the study period. We present unadjusted coverage rates by type of insurance and uninsurance rates for the pre period—2010–13, before the implementation of the ACA’s main coverage reforms. All estimates were population weighted, and standard errors were clustered at the state level.

One of the underlying assumptions of our interrupted time-series models was that the composition of our sample and relevant groups (that is, part-time versus full-time workers in expansion versus nonexpansion states) did not change after health reform. Consistent with the literature that found little labor-market effects,^5,6 we found no evidence of composition changes (appendix exhibit 3).⁴

Limitations

Our study had several limitations. First, we tested the parallel-trend assumption by evaluating pre-period trends by work hours and expansion-state status, and we found mostly nonsignificant differences in those trends (appendix exhibits 10 and 11).⁴ The only exception was other private insurance, which could reflect the smaller number of workers with this type of coverage in our sample.

Second, the employer mandate did not take effect until 2016 for employers with 50–99 full-time equivalent (FTE) employees, which was after our study period. This means that our findings could underestimate the overall changes associated with ACA-related health reform.

Study Results

Changes In Work-Hours Insurance Gaps

Postreform changes in coverage differed by work hours and state expansion status in 2015 (exhibit 1; results for 2014 are shown in appendix exhibit 4).⁴ The largest declines in uninsurance rates were concentrated among part-time workers (declines of 12.4 percentage points and 13.3 percentage points in nonexpansion and expansion states, respectively). While coverage increased by very similar amounts, the composition of this change differed greatly between these two sets of states. In nonexpansion states, other private (primarily Marketplace) insurance increased by 10.1 percentage points among part-time workers, with very small (and nonsignificant) changes in Medicaid and employer-sponsored insurance. In expansion states, the increase in Medicaid coverage among part-time workers was large (18.0 percentage points), but this increase was partially offset by a reduction in employer-sponsored insurance. Among full-time workers, we observed similar but more modest changes in coverage, except for employer-sponsored coverage, which increased among full-time workers while decreasing among those working part time.

Changes In Eligibility For And Take-Up Of Employer-Sponsored Insurance

For full-time workers in both expansion and nonexpansion states, the increase in employer-sponsored insurance coverage was driven by increased eligibility, with take-up holding constant (exhibit 2). In contrast, for part-time workers in expansion states, declines in employer-sponsored insurance were not the result of declines in eligibility (a pattern we would expect if employers had dropped insurance offers to part-time workers in response to newly available public or subsidized private coverage). Rather, they were the result of reductions in take-up.

Coverage Gaps Between Part- And Full-Time Workers Before 2014

Full-time workers were more likely to have employer-sponsored insurance (81.8 percent) in 2010–13, compared to part-time workers (53.2 percent)—primarily reflecting well-known differences in employer-sponsored insurance offer rates by work hours (exhibit 3).^1–3 A likely result of this difference is that the rate of other private insurance was greater for part-time workers (5.4 percent), compared to full-time workers (1.4 percent). Part-time workers were more likely to have Medicaid (9.4 percent), compared to full-time workers (2.2 percent). Finally, part-time workers were slightly more than twice as likely to be uninsured relative to their full-time counterparts (29.6 percent versus 14.3 percent).

SOURCE Authors’ analysis of data for 2010–13 from the Medical Expenditure Panel Survey–Household Component. NOTES The population, full and part time, and employer-sponsored insurance are explained in the notes to exhibit 1. Estimates incorporate sample weights, and the estimates for full- and part-time workers are significantly different ($p<0.05$) for all types of coverage.

Discussion

Our findings highlight the substantial uninsurance disparities by work hours that existed before the 2014 health reform and the extent to which these disparities narrowed after 2014.^1–3 While insurance inequality between full- and part-time jobs remains in the postreform era, it diminished in the years following the ACA insurance expansions. Our findings echo those of prior studies,^7–9 as we found that Medicaid played a large role in reducing uninsurance rates in expansion states, whereas reduced uninsurance rates in nonexpansion states were more attributable to increases in private Marketplace coverage.

Despite fears about employers’ dropping coverage for part-time workers,^10,11 we found that part-time workers’ eligibility did not decline in a widespread fashion, at least through 2015. On the other hand, eligibility among full-time workers increased, possibly reflecting large employers’ compliance with the ACA employer mandate.

Another finding was that ACA reforms might have crowded out employer-sponsored insurance among part-time workers in states that expanded Medicaid. Prior studies of crowd-out have found mixed results,⁸ with most finding little evidence of an effect. We further showed that the reduction in employer-sponsored insurance for this group reflected declines in take-up, rather than in eligibility. This decline in take-up could reflect high out-of-pocket expenses, including premiums, for employer-sponsored insurance, relative to the incomes of low-income workers.¹² Future research should examine whether these trends extend into 2016, when firms with 50–99 FTEs were required to offer insurance to full-time workers. Additionally, our findings contrast with those of a recent study that found stable offer and take-up rates for low-income workers after the Medicaid expansion.⁹

Conclusion

Four years after the full implementation of the ACA, uncertainty regarding future coverage rules still exists. Assessing the impact of insurance expansions on groups of American workers who lack access to employer-sponsored insurance, such as part-time workers, is crucial for ongoing policy discussions. Part-time work is an involuntary employment status for millions of American workers.³ One in four part-time American workers live in poverty, and many people and families rely on a part-time job as their sole source of employment.^2,3 Our findings demonstrate the importance of examining coverage gaps by work hours and Medicaid expansion status, which is a new contribution to the large literature on the impacts of the ACA implementation.⁸

ACKNOWLEDGMENTS

The views expressed in this article are those of the authors, and no official endorsement by the Department of Health and Human Services or the Agency for Healthcare Research and Quality is intended or should be inferred. The authors thank Tom Selden, Joel Cohen, Ed Miller, and Jessica Vistnes for their feedback.

NOTES

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