Any change in the health insurance market could prompt a reaction by employers in what kind and at what cost they offer coverage. This policy brief examines the research on employer decision-making. Key findings include: Firms are most likely to offer plans that respond to the preferences of their most valuable, hard-to-retain workers. Firms are more likely to offer health insurance if they employ high-wage workers; if they are unionized; or if they are in the manufacturing or public sectors. While theory suggests that employers will shift the cost of premiums to employees in the form of lower wages, this is not the case in practice. There are serious gaps in research, including: an absence of detailed data about individuals; little information about earnings distribution; ages and other characteristics within firms of different sizes; and little study of employer behavior.