Donald Marron acknowledges that Mitt Romney’s tax reform proposal can’t accomplish all its stated objectives, but treats the plan as a starting point for negotiation rather than an attack on the middle class.

The Tax Policy Center’s latest research report went viral earlier this month, drawing attention in the presidential campaign and sparking a constructive discussion of the practical challenges of tax reform. Unfortunately, the response has also included some unwarranted inferences from one side and unwarranted vitriol from the other, distracting from the fundamental message of the study: tax reform is hard.

The paper, authored by Sam Brown, Bill Gale, and Adam Looney, examines the challenges policymakers face in designing a revenue-neutral income tax reform. It illustrates the importance of the tradeoffs among revenue, tax rates, and progressivity for the tax policies put forward by presidential candidate Mitt Romney. It found, subject to certain assumptions discussed below, that any revenue-neutral plan along the lines Governor Romney has outlined would reduce taxes for high-income households, requiring higher taxes on middle- or low-income households. Perhaps that’s not his intent, but it is what we can tell about his plan so far. (A more detailed analysis would be possible, of course, if and when Governor Romney provides more details.)

The paper is the latest in a series of TPC studies that have documented both the promise and the difficulty of base-broadening, rate-lowering tax reform. Last month, for example, Hang Nguyen, Jim Nunns, Eric Toder, and Roberton Williams documented just how hard it can be to cut tax preferences to pay for lower tax rates. An earlier paper by Dan Baneman and Eric Toder documented the distributional impacts of individual income tax preferences.

The new study applies those insights to Governor Romney’s tax proposal. To do so, the authors had to confront a fundamental challenge: Governor Romney has not offered a fully-specified plan. He has been explicit about the tax cuts he has in mind, including a one-fifth reduction in marginal tax rates from today’s level, which would drop the top rate from 35 percent to 28 percent and a cut in capital gains and dividend taxes for families with incomes below $200,000. He and his team have also said that reform should be revenue-neutral and not increase taxes on capital gains and dividends. But they have not provided any detail about what tax preferences they would cut to make up lost revenue.

As a political matter, such reticence is understandable. To sell yourself and your policy, it’s natural to emphasize the things that people like, such as tax cuts, while downplaying the specifics of who will bear the accompanying costs. Last February, President Obama did the same thing when he rolled out his business tax proposal. The president was very clear about lowering the corporate rate from 35 percent to 28 percent, but he provided few examples of the tax breaks he would cut to pay for it. Such is politics.

For those of us in the business of policy analysis, however, this poses a challenge. While analysts such as TPC strongly prefer to analyze complete plans, that sometimes isn’t possible. They must provide what information they can with the resources available. Earlier this year, for example, TPC analyzed the specified parts of Governor Romney’s proposal and documented how much revenue he would have to make up by unspecified base broadening (or, possibly, macroeconomic growth) and how the rate cuts would affect households at different income levels.

The latest study asked a different question: Could Romney’s plan maintain current progressivity given revenue neutrality and reasonable assumptions about what types of base broadening he’d propose? There are roughly $1.3 trillion in tax expenditures out there, but not all will be on Governor Romney’s list. He has said, for example, that raising capital gains and dividend taxes isn’t an option and has generally spoken about lowering taxes on saving and investment. Based on those statements, the authors considered what would happen if Romney kept all the tax breaks associated with saving and investment, including not only the lower rates on capital gains and dividends, but also the special treatment for municipal bonds, IRA and 401ks, and certain life-insurance plans, as well as the ability to avoid capital gains taxes at death (known as step-up basis). The authors also recognized that touching some tax breaks is beyond the realm of political possibility, such as taxing the implicit rent people get from owning their own home.

Given those factors, the study then examined the most progressive way of reducing the other tax breaks that remain on the table—i.e. it rolls them back first for high-income people. But there aren’t enough of those preferences to offset the benefits that high-income households get from the rate reductions. As a result, a revenue-neutral reform within these constraints would cut taxes at the high-end while raising them in the middle and perhaps bottom.

What should we infer from this result? Like Howard Gleckman, I don’t interpret this as evidence that Governor Romney wants to increase taxes on the middle class in order to cut taxes for the rich, as an Obama campaign ad claimed. Instead, I view it as showing that his plan can’t accomplish all his stated objectives. One can charitably view his plan as a combination of political signaling and the opening offer in what would, if he gets elected, become a negotiation.

To get a sense of where such negotiation might lead, keep in mind that Romney’s plan is not the first to propose a 28 percent top rate. The Tax Reform Act of 1986 did, as did the Bowles-Simpson proposal and the similar Domenici-Rivlin effort (on which I served). Unlike Governor Romney’s proposal, all three of those tax reforms reflect political compromise. And in all three cases, part of that compromise was eliminating some tax preferences for saving and investment, which tend to be especially important for high-income taxpayers. In particular, all three reforms resulted in capital gains and dividends being taxed at ordinary income tax rates.

TPC’s latest study highlights the realities that lead to such compromises.

*Republished from author’s blog.

The views expressed in this article are the author's own and do not necessarily reflect Fair Observer’s editorial policy.