This benchmark/bidding/rebate process accounts for from 97% to 100% of the cost of the given Medicare Advantage plan to the Medicare Trust Funds. The individual fee for each Part C beneficiary is also uplifted or downsized slightly (approximately 1%-3% in either direction on average) from the county-specific fee based on a risk-based formula tied to the personal health characteristics of the capitated individual. The theory is that the risk-based formula will not affect spending, but in practice it almost always increases cost per beneficiary by one or two percent, either because the Medicare Advantage plan is diligent in upcoding to a beneficiary's specific risks or because patients on FFS Medicare, where providers have no incentive to code at all, are undercoded. Based on the 2019 benchmark/bidding/rebate process, the Medicare Advantage average monthly plan premium in 2020 is estimated to decrease 14 percent to $23.00 from an average of $26.87 in 2019. Since 2017, the average monthly Medicare Advantage premium has decreased by an estimated 27.9 percent. This is the lowest that the average monthly premium for a Medicare Advantage plan has been since 2007 right after the second year of the benchmark/framework/competitive-bidding process. But these averages mask wide regional and beneficial differences. Just as the most important benefit of Part C plans is the annual out of pocket spend protection, the major determinant of monthly premium differences is the size of that protection. By law, a Part C beneficiary cannot spend more than $6700 out of pocket annually on medical services; it is plans with this limit that have the lowest premiums. Conversely, some Part C plans have OOP limits as low as $1500 annually but of course -- for these plans -- the premium is higher. The average OOP limit in 2018 was around $5000. Note that an OOP limit is not a deductible as is often reported. It is just the opposite of a deductible; it is a financial-protection upper-bound. It is rare for a Medicare Advantage beneficiary to reach the annual OOP limit but it provides a stop-loss feature that is also found in most private health insurance but not in "Original Medicare." Medicare Parts A and B provide no similar OOP spending cap and the exposure of a Medicare Part A and/or B beneficiary to a financial catastrophe is unlimited (but also rare). Once the OOP maximum is reached for an individual under a Part C health plan, the plan pays 100% of medical services for the remainder of the calendar year.