Personalized Telephone Outreach Increased Health Insurance Take-Up For Hard-To-Reach Populations, But Challenges Remain.

We tested the impact of personalized telephone calls from service center representatives on health plan enrollment in California's Affordable Care Act Marketplace, Covered California, using a randomized controlled trial. The study sample included 79,522 consumers who had applied but not selected a plan. Receiving a call increased enrollment by 2.7 percentage points (22.5 percent) overall. Among subgroups, receiving a call significantly increased enrollment among consumers with income below 200 percent of the federal poverty level (4.0 percentage points or 47.6 percent for consumers with incomes below 150 percent of poverty and 4.0 percentage points or 36.4 percent for consumers with incomes of 150-199 of poverty), as well as those who were referred from Medicaid (2.9 percentage points or 53.7 percent), those ages 30-50 (2.4 percentage points or 23.3 percent) or older than age 50 (5.1 percentage points or 34.2 percent), those who were Hispanic (2.3 percentage points or 31.1 percent), and those whose preferred spoken language was Spanish (3.2 percentage points or 74.4 percent) or English (2.6 percentage points or 18.6 percent). The intervention provided a two-to-one return on investment. Yet absolute enrollment in the target population remained low; persistent enrollment barriers may have limited the intervention's impact. These findings inform implementation of the American Rescue Plan Act of 2021, which expands eligibility for subsidized coverage.