Final answer:
The factor used to calculate the monthly premium for Medicare Part B beneficiaries is income level.
Step-by-step explanation:
The factor used to calculate the monthly premium for Medicare Part B beneficiaries is income level. Medicare Part B is an optional insurance system that covers healthcare costs outside of hospital stays for physician services, medical tests, and outpatient visits. Beneficiaries pay a monthly fee, deductible charges, and copayments, and the government contributes about three-fourths of the overall costs.
The more a beneficiary earns, the higher their premium may be, as the premium is set to be proportional to the cost burden on the system. This structure ensures that Medicare remains sustainable and accessible to those who need it the most.