"The [GAO report] ... is both one of the clearest and most succinct descriptions of how coordination is supposed to work between the [IRS] and the ACA marketplaces in administering the ACA's premium tax credit and individual responsibility penalty, and the best description of how that coordination in fact functioned in the 2014 tax filing season, in 2015.... [On] the whole [the report] shows a program with much room for improvement.... [ASPE reports that the] benchmark plan premium growth between 2014 and 2015 was 8.4 percentage points lower in counties that saw a net gain in insurers than in other counties, with each net gain of one insurer associated with a 2.8 percentage point reduction in the rate of growth of the benchmark premium."