(CNN) Obamacare rates are going up next year.

The premium for the benchmark Obamacare silver plan is projected to jump an average of 15% next year, according to a Congressional Budget Office report released Wednesday.

The increase is being driven in large part because people will no longer be penalized for not having insurance, as of 2019. Congress eliminated the penalty associated with Obamacare's individual mandate as part of its tax reform package last year.

This change alone will cause premiums to be 10% higher because fewer healthy people will buy coverage, leaving insurers with a sicker and costlier group of policyholders, the CBO projected.

Going forward, the agency projects premiums will increase an average of 10% a year between 2019 and 2023 and then 5% annually between 2024 and 2028. Most of those who buy coverage on the Obamacare exchanges are shielded from these rate hikes because they receive federal subsidies.

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