Here is the Trump administration’s estimate of the benefit of USMCA (aka NAFTA 2.0), the trade deal with Mexico and Canada that was concluded last year. They say that GDP will go up:
OK, it’s a table, not a chart. Sue me. In any case, it claims that Trump’s new trade deal will increase GDP by 0.35 percent, but mysteriously doesn’t say when this increase will happen. I wonder why they’d leave that out?
The answer is that it’s because this increase happens over the course of 16 years. That’s about 0.02 percent per year. Just to make it clear what that means, it’s the equivalent of $100 growing by two cents.
But wait, there’s more! It turns out that the model used by the International Trade Commission actually projects a GDP decrease of 0.12 percent. However, they add 0.47 percentage points because “commitments in USMCA address  regulatory uncertainty by providing assurance to firms that current conditions will be maintained into the future.” The idea here is that companies can’t really be sure that things we’ve all been doing for decades will continue in the future, and the new treaty clears up this uncertainty.
Maybe so. But if that’s really the case, maybe we should sign a treaty that just clears up the regulatory uncertainty and leaves everything else alone?
This all comes via Dean Baker, who has more to say here.