Friday, December 21, 2018

About that "late enrollment surge"

At the end of Week 6 of Open Enrollment for 2019 in the 39 states that use HealthCare.gov, all-state enrollment, at 4,132,432, was 88.3% of the Week 6 total for 2018.

By the end of Week 7, the final week, the 2019 total (8,454,882) was 95.8% of the 2018 total. Surprise! News stories reference a late enrollment surge. But the surge was a mirage -- generated by a slight difference in the weekly breakdown of an enrollment season that was 45 days in both years. Or rather, the surge was normal and happens every year -- this year the pace did not accelerate more than last.

In CMS's weekly enrollment snapshots, "Week 1" had four days in November 2017 and three days in November 2018. "Week 7," conversely, had six days in December 2017 and seven days this December.

Enrollment season starts slowly and ends fast. This year, enrollments averaged 123,892 per day in Week 1 and 617,493 in Week 7. More than half of all enrollment -- 51% -- happened in the final week (boosted by about 1.7 million auto-enrollments or passive renewals, added in at the end). Last year, 47% of enrollees were booked in the final (6-day) week.

Through Week 6, this year's tally was short a day that roughly equalled 1.4% of the end total. The extra day in the final week, conversely, was worth 7.3% of the total. Thus - hey presto -- the year-over-year apparent enrollment drop shrank from 11.7% to 4.2% -- notwithstanding that per-day enrollments in Week 7 this year were just 89% of last December's per diem total (617,493 vs. 690,661).

I was tempted to suggest that enrollment this year got an "extra day" -- or rather, four fifths of one, "trading" a day in early November for a day in mid December "worth" five times as much. But that can't be right. Open enrollment has its own rhythm, mostly accelerating weekly, though with a pause in the middle. To really compare rhythms between two years, you'd have to line up daily totals side-by-side.

Maybe someone will do that. But for now, let's dispense with the myth that enrollment surged late in 2018.

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Program note: to check out weekly enrollment totals, google "Weekly Enrollment Snapshot Week X 2017 2018. They come right up.

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