But how that will work in practice for any given insurer is, at this point, uncertain. And CareFirst, even more than its competitors, has a reason to assume something like the worst-case scenario. The Affordable Care Act puts limits on year-to-year rate increases, which gives insurers an incentive to high-ball their proposals now. If they charge too much next year, they can — and would be required to — provide rebates to their customers. If they charge too little, they might never really be able to catch up.