ADP officials said the findings of the ADP Research Institute study were based on actual, real-world data for approximately 1 million employees and more than 2 million covered lives.
The study said 88 percent of the full-time workforce was eligible for benefits but 77 percent of the eligible full-time employees actually selected health coverage. The result was 68 percent of the total full-time workforce was covered by employers' health plans.
The average employer within the ADP Benefits Study contributed $7,225 a year in health premiums for each employee who enrolled in the employer's group health plans for benefit year 2012.
"Unlike survey-based studies, the data in our study was derived from the actual, aggregated and anonymous benefits data and enrollment administration activity of large ADP clients representing multiple industries across all 50 U.S. states," Tim Clifford, president of ADP Benefits Administration Services, said in a statement.
Despite wide disparities in total premium costs on an employer-by-employer basis, very large employers of more than 5,000 employees as a group paid 14 percent less for health insurance than employers with smaller populations of 1,000 to 2,499 employees. The benefits of these lower premium costs were shared equally by employer and employee, the study said.
The study was based on employee data from a subset of ADP's health and welfare benefits clients of approximately 300 U.S. organizations that employed more than 1,000 workers. All states and major industries were represented, as well as gender, age and marital status.