Worst changes in enrollment, based on CMS billable month data. (We divided the billable month figures by 12.) To see more ACA exchange enrollment data cards, click on the arrow on the right side of the gallery box above. It's official: The market for individual major medical coverage that complies fully with the Affordable Care Act went through an economic car wash in 2017. Total enrollment fell about 11%, and the typical monthly premium that an issuer charged increased about 21%. The Centers for Medicare and Medicaid Services has told the story in a new batch of data.

The data

CMS prepares the individual major medical data every year, to run the ACA risk-adjustment program. The program uses cash from issuers that end up with low-risk enrollees to compensate issuers that end up with more than their fair share of the high-risk enrollees. Annual CMS spreadsheets give each state's average monthly premium, and each state's total "billable months." (A user can convert the billable month total into an annual enrollment figure by dividing that number by 12.) CMS has published comparable risk-adjustment data for both 2016 and 2017 for the District of Columbia, and for all states but Hawaii, Massachusetts and Vermont. CMS has actually published 2017 data for Hawaii, although comparable data was missing in the 2016 spreadsheet: Hawaii had average monthly premiums of $477 in 2017, and annualized individual major medical enrollment of about 33,000. The premium figures represent the full amounts that the issuers actually charge. The figures do not include the effects of any ACA premium tax credit subsidies or other subsidies that might have cut the enrollees' out-of-pocket premium spending. The version of the spreadsheet on the CMS website gives data produced by the federal government. Because the federal government produced the data, and posted it on a public website, agents, insurers and others can use the data in their own reports, articles and social media posts without worries about copyright restrictions.

What CMS found

CMS found that:

• Total individual major medical enrollment in the jurisdictions included fell 11%, to about 12.7 million.
• The enrollment decrease ranged from a drop of 37%, in one state, to an increase of 2%, in Arkansas and Delaware.
• The typical state's average monthly premium increased 21%. Half had increases about the size or lower, and half had increases about that size or lower.
• The average premium change ranged from a low of close to zero, in North Dakota, to a high of 99%, in Arizona.
• The median statewide average monthly premium was $466.
• State's statewide average monthly premiums ranged from $336 in Utah, to $1,048, in Alaska.

We posted a collection of data cards above that show the states with the five most dramatic drops in individual major medical enrollment. Look below for a table showing what happened in all of the jurisdictions included in both the 2016 and 2017 spring risk-adjustment market data spreadsheets.