Researchers related the trend to decreasing overall employment, as well as rising healthcare costs.
According to the study, the average annual premium for individuals with work-based coverage doubled in the last decade from about $2,500 to about $5,000.
Family premiums rose even more sharply, from about $6,400 on average to about $14,500.
"Everyone’s costs have increased dramatically,” said Risa Lavizzo-Mourey, RWJF's president and CEO, in a statement.
"Higher costs naturally translate into fewer employers offering insurance coverage, and fewer employees accepting it, even when it is offered."
States with the sharpest declines have struggled with industry upheaval.
Michigan's rate of employer-based insurance fell about 15 percent in the 2000s, for example, placing it at the top of the list.
The study was prepared by researchers at the University of Minnesota’s State Health Access Data Assistance Center.
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