CMS has issued a new report on the impact of the ACA on health spending overall and on the number of uninsured, and Politico is very helpfully hosting the document. It begins with the following caveats:

Except where noted, we have not estimated the impact of the various tax and fee provisions or the impact on income and payroll taxes due to economic effects of the legislation. Similarly, the impact on Federal administrative expenses is excluded.

That is, the analysis assumes that the increase in implicit marginal tax rates will have no consequences and that the Federal government will not have to increase its expenditures to manage a complex new set of tax subsidies. The caveats continue:

Additionally, we assume that employers and individuals would take roughly 3 to 5 years to fully adapt to the new insurance coverage options and that the enrollment of additional individuals under the Medicaid coverage expansion would be completed by the third year of implementation. Because of these transition effects and the fact that most of the coverage provisions would be in effect for only 6 of the 10 years of the budget period, the cost estimates shown in this memorandum do not represent a full 10-year cost for the new legislation.

The CMS also another useful caveat:

The actual future impacts of the PPACA on health expenditures, insured status, individual decisions, and employer behavior are very uncertain. The legislation would result in numerous changes in the way health care insurance is provided and paid for in the U.S., and the scope and magnitude of these changes are such that few precedents exist for use in estimation. Consequently, the estimates presented here are subject to a substantially greater degree of uncertainty than is usually the case with more routine health care legislation.

One potential source of confusion in the document is that it conflates national health expenditures with federal health expenditures. This creates the impression that firms and individuals will pay nothing beyond new taxes and fees to yield the coverage expansion. For example, Ezra Klein writes:

So that’s the bottom line of the report: We’re covering 34 million people and come 2019, spending is expected to be one percentage point — and falling — above what it would’ve been if we’d done nothing.

But what is the relevant baseline? If it is federal health expenditures, surely a measure that included the mandated spending that private individuals must engage in or face a penalty ought to be factored in as well.

We could also impose a mandate that creates a far more onerous penalty and offers no subsidies at all. This would lead, one assumes, to even lower federal health expenditures and an impressive coverage expansion. But of course we wouldn’t characterize this as a policy triumph.