Premium increases would have been even higher in 2003--an estimated average 18%--if not for increased consumer cost-sharing through higher deductibles, copayments and coinsurance, the study said.

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Traditional Medicare does cover most necessary medical concerns and is accepted by most medical professionals across the U.S. However, most original Medicare enrollees do purchase supplemental coverage to pay for deductibles, coinsurance, and other out-of-pocket costs.

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