As premiums for Affordable Care Act (ACA) insurance plans skyrocketacross the country, the Department of Health and Human Services (HHS) appears to be spinning the bad news by noting that 2017 premiums are about what the Congressional Budget Office (CBO) expected they would be when the law passed in early 2010. However, CBO’s November 2009 estimate of future premiums involved significant and generally unforeseeable errors in key underlying assumptions having nothing to do with the ACA. A valid understanding of the ACA’s effect on insurance premiums would need to account for these errors.

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