Insurers have told state regulators that they covered only 13.5 million people in 1.1 million small-group plans in 2015, according to analysts at the firm.
The number of small employer plans was 12 percent lower than it was in 2014, and 25 percent lower than it was in 2013, the analyst say.
The number of people covered by the plans was 6.9 percent lower than in 2014, and 19 percent lower than in 2013.
The analysts came up with those figures by analyzing the Supplemental Health Care Exhibit forms that insurers filed with state insurance regulators.
News reports suggest that some smaller employers are trying to run self-insured health plans, and the supplemental exhibit figures do not include any information about small self-insured plans, the analysts note.
The analysts do not provide small-group enrollment and case-count data from before 2013, and analysts have noted in other reports that small-group enrollment was shrinking steadily in the years before Congress began debating the Affordable Care Act.
Elsewhere in the 2015 small-group update, the analysts say:
137 carriers offered about 277 small-group health plans that had 1,000 or more enrollees in 2015.
The five top carriers in the small-group market cover about 48 percent of all enrollees in fully insured small-group plans.
Two of the biggest carriers in the market combined for an $830 million underwriting profit in 2015.
About 55 percent of the 2.1 million employers with five or more employees offer some kind of health coverage, but only 21 percent of the workers at those employers have fully insured major medical coverage.
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