Insurance rates are based on the risk pool you fall into. When companies are purchasing plans for health insurance, the company as a whole is placed into a risk pool. Since you are dealing with a large group of people, in general the risk pool is lower for the company, then if each person was evaluated individually. Hence a company can achieve lower rates then an individual. And generally the bigger the company, the lower the rates. An individual purchasing would have to pay significantly higher rates for comparable coverage that they would if they were in a large company.