Article Title

Medicaid Expansion and the Affordable Care Act: Data From the First Year of Enrollment at Kaiser Permanente Northern California

Publication Date



Medicaid expansion, Affordable Care Act


Background/Aims: The Affordable Care and Patient Protection Act (ACA) aims to reduce rates of un-insurance partly through expansion of Medicaid eligibility and the establishment of insurance exchanges with income-based subsidies. While prior studies used historical enrollment data to predict the characteristics and utilization patterns of newly eligible Medicaid recipients, few studies to date have actively analyzed these new enrollees. By providing Medi-Cal coverage and commercial insurance, Kaiser Permanente provides a unique perspective when analyzing these programs. As part of a larger ongoing study, we aim to provide early data on the characteristics and preliminary utilization patterns of new Medi-Cal enrollees after the roll-out of insurance expansion under the ACA.

Methods: This is a descriptive study including two distinct cohorts of adult (18–64) Kaiser Permanente Northern California (KPNC) members who were newly enrolled in KPNC Medicaid in 2013 and 2014, defined as no KPNC enrollment in the prior 12 months.

Results: Between 1/2014 and 6/2014, 9,795 adults enrolled in Medi-Cal while 5,322 enrolled in 2013. Compared to enrollees in 2013, Medi-Cal enrollees in 2014 were older (44% aged 41–64 vs. 29.2%). New enrollees were predominantly female (58.7% female vs. 41.3% male), but less so than in 2013 (62.2% female vs. 37.8% male). 2014 enrollees were proportionally less likely to be white (29.0% vs. 30.0%), black (15.3% vs. 24.5%) or Hispanic (17.0% vs. 27.8%), and proportionally more likely to be Asian (10.2% vs 9.7%). However, a larger percentage was classified as “unknown” (26.8% vs 6.2%). Preliminary rates of utilization (per member per month) were similar, except for outpatient visits where the mean for the post-ACA cohort was 0.98 (1.59) relative to 0.74 (0.94) for the pre-ACA cohort.

Discussion: Consistent with expectations, newly enrolled Medi-Cal beneficiaries post-ACA were older and less predominantly female. However, there also was a decrease in race/ethnicity ascertainment in the post-ACA cohort. Additional analysis will explore differences in utilization once a full year of data for the 2014 cohort has been collected. When combined with data on medical comorbidities of this population, this study will help further understand the needs of the newly insured post-Medicaid expansion.




April 6th, 2015


April 28th, 2015