The Economist has a piece on macroeconomic models used to evaluate tax policy.
Lurk near PhD economists online or at conferences, and you will hear them talk about “crisis in macro”. They mean that the models and assumptions most dominant among macroeconomists have failed repeatedly since 2007 to predict or even describe what’s happening. A defence, popular among academics, goes like this: we did get it wrong, but as responsible social scientists, we’re busy and fascinated right now, trying to figure out what was broken and how to fix it. It is a fair defence. In particular young macroeconomists have been using bigger datasets and faster computers to more accurately predict human behaviour. Economists are more likely to accept now, for example, that people with and without access to credit or wealth react differently to the same policy, an idea that is slowly working its way into models at central banks and even at the Joint Committee on Taxation.
This progress is unfortunate for Republicans. In the 1990s social science was on their side. Because data and computing power were harder to come by, macroeconomic models relied on thought experiments. The seminal model showing the ideal capital-gains tax rate as zero, for example, dates to 1986. It assumes that the economy consists of only one person. Also, she is immortal. The Wonder Woman economy, if you will. That model is now interesting only for a lecture on the history of economic thought. We’ve moved on, macroeconomists protest. But economists have. And Republicans haven’t…
But if you are going to insist on modeling the future and then planning around it, you have to do it right. The economists at the Joint Committee on Taxation are thoughtful. They read the most recent research. They examine their own models and, when they can, update them—conservatively. If, as Republicans have been insisting for 20 years, we have to assess our tax policies with dynamic scoring, there is no better way to do it than through the JCT. Unfortunately, as modeling has improved, it has not improved in the direction Republicans prefer, which leaves them where they are now. They wanted social science in policy-making, and they got it, in the form of a $1trn tax bill.
I don’t know how any ethical person can support the Republican party right now. They don’t care about facts, logic, or evidence, and certainly not economic growth or raising the living standards of their constituents. They are blantantly and shamelessly committed to lining the pockets of their big-business funders. It’s corrupt, undemocratic and shameful.