This is one of a series of guest TaxVox blog posts discussing dynamic scoring. The House recently changed the rules of budget scoring: The Congressional Budget Office and the Joint Committee on Taxation will now account for macroeconomic effects when estimating the budget impacts of major legislation. Here are three things you should know as we await the first official dynamic score. 1.   Spending and regulations matter, not just taxes You might think dynamic scoring is just about taxes. It’s not. Spending and regulatory policies can also move the economy. Take the Affordable Care Act. CBO estimates that the law’s insurance subsidies will reduce labor supply by 1.5 to 2.0 percent from 2017 to 2024, some 2 to 2.5 million full-time equivalent workers. If CBO and JCT do a dynamic score of the House’s latest ACA repeal, this effect will be front and center. The same goes for immigration reform. In 2013 (and in 2006), CBO and JCT included some macroeconomic effects in their score of comprehensive immigration reform, though they did not do a fully dynamic score. Under today’s rules, reform would show an even bigger boost to the economy and more long-term deficit reduction than the agencies projected in the earlier bills. 2.   Dynamic scoring isn’t new For more than a decade, CBO and JCT have published dynamic analyses using multiple models and a range of assumptions. For example, JCT projected former House Ways & Means Committee chairman Dave Camp’s tax reform plan would boost the size of the economy (not its growth rate) by 0.1 to 1.6 percent over 2014 to 2023. The big step in dynamic scoring will be winnowing such multiple estimates into the single set of projections required for official scores. Observers understandably worry about how the scorekeepers will do that. For example, what will JCT and CBO do with certain forward-looking models that require assumptions not just about the policy in question but also about policy decisions Congress will make in the future? If the agencies score a tax cut today, do they also have to include future tax increases or spending cuts to pay for it, even if Congress doesn’t specify them? If so, how should the agencies decide what those offsetting policies are? Does the existence of such models undermine dynamic scoring from the start? Happily, we already have a good sense of what the agencies will do, and no, the existence of such models doesn’t hamstring them. At least twice a year, CBO and JCT construct baseline budget projections under existing law. That law often includes scheduled policy changes, most notably the (in)famous “fiscal cliff” at the end of 2012. CBO and JCT had to include the macro effects of the cliff in their budget baseline at that time, even though they had no idea whether and how Congress might offset those policies further in the future. That’s dynamic scoring in all its glory, just applied to the baseline rather than analyzing new legislation. CBO and JCT didn’t need to assume hypothetical future policies to score the fiscal cliff, and they won’t need to in scoring legislation either. 3.   Dynamic scoring won’t live up to the hype, on either side Some advocates hope that dynamic scoring will usher in a new era of tax cuts and entitlement reforms. Some opponents fear that they are right. Reality will be more muted. Dynamic scores of tax cuts, for example, will include the pro-growth incentive effects that advocates emphasize, leading to more work and private investment. But they will also account for offsetting effects, such as higher deficits crowding out investment or people working less because their incomes rise. As previous CBO analyses have shown, the net of those effects often reveals less growth than advocates hope. Indeed, don’t be surprised if dynamic scoring sometimes shows tax cuts are more expensive than conventionally estimated; that can easily happen if pro-growth incentives aren’t large enough to offset anti-growth effects. Detractors also worry that dynamic scoring is an invitation for JCT or CBO to cherry pick model assumptions to favor the majority’s policy goals. Doing so runs against the DNA of both organizations. Even if it didn’t, the discipline of twice-yearly budget baselines discourages cherry picking. Neither agency wants to publish rosy dynamic scenarios that are inconsistent with how they construct their budget baselines. You don’t want to forecast higher GDP when scoring a tax bill enacted in October, and have that GDP disappear in the January baseline. I am cautiously optimistic about dynamic scoring. Done well, it can help Congress and the public better understand the fiscal effects of major policies. There are still some process issues to resolve, most notably how investments might be handled, but we should welcome the potential for better information. Donald Marron is director of economic policy initiatives at Urban Institute. He was acting director of the Congressional Budget Office in 2006 and a member of the White House Council of Economic Advisers in 2008-2009.