It probably comes as no surprise that cost of firm sponsored health plans are the largest employment cost after salary. The average firm spends $7,983 per employee, up 6.1 percent from last year. Although the growth is far less than the 15% increases earlier in the decade, it is still going up at twice the rate of inflation. According to a Mercer Associates survey, 34 percent of employers in all sectors make same sex domestic partner coverage available, up from 29% last year.