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.