Final answer:
Employers offer group insurance because it a) costs less than individual insurance due to insurers' ability to negotiate lower rates with providers and mitigate adverse selection with a diverse insured group.
Step-by-step explanation:
The question at hand is asking for one reason why employers offer group insurance as a benefit. The correct answer to this question is (a) Costs less to purchase than individual insurance. This is because when insurance companies manage a large pool of clients, such as those covered by an employer's group insurance plan, they gain leverage to negotiate for lower rates with health care providers compared to what individuals could secure on their own. This collective bargaining power increases the benefit to the insured individuals and also saves the insurance company money on claim payouts.
In addition, by selling insurance through an employer, insurance companies can pool together a diverse group of individuals with varying health risks. This diversification helps to mitigate the impact of adverse selection, which occurs when there is a possibility of only high-risk individuals seeking out insurance coverage, thus raising costs for the insurer. Many employers offer group insurance plans not only to secure lower costs but to ensure a broad mix of insured individuals, thereby stabilizing the risk pool.