Employer-sponsored health insurance covers almost 159 million non-elderly US workers and their dependents, and employees and jobseekers alike view group health coverage as the single most important non-cash job-related benefit. The enactment of the Affordable Care Act (ACA) in 2010 led to a sharp increase in employers self-funding their group health plans, with the market tripling in size in the decade that followed. Large employers (e.g., with more than 500 employees) can, and for the most part do, self-fund their group medical coverage in a relatively efficient manner. Self-funding gives these groups transparency and a measure of control over plan design and operation. But because self-funding relies on the law of large numbers for its efficacy, it does not work well, or at all, for smaller employers. The latter must usually look to commercial group health insurance. For groups of 50 employees or less, this usually means the small group markets, which tend to be opaque and expensive.