Here is an exchange from a New Zealand parliamentary hearing on the TPP:
Clark: On that point, the non-tariff barrier portion of the argument—the analysis, or the modelling, seems to have gone to a view that, crudely characterised as “Think of a number and then halve it.” in terms of the benefits of those changes that are projected in the model. Do you consider that a robust approach?
Walker: The modelling work that we had done came up with a certain set of numbers, based on some assumptions that the modellers had looked at about what the agreement might result in, in those areas. What we did, in terms of presenting the result to the Government, was we took a conservative view, and therefore we halved that number. So we took a conservative view of what those independent modellers were telling us.
Clark: So a number, halved. I’ll put it to you, that a number—if it’s got nothing behind it of any substance—halved is still a number with behind it without any substance. And that is the majority of the benefits projected in your cost-benefit analysis.
Walker: I didn’t say the number had no substance behind it. I said we deliberately took a very conservative view in how we presented that part of the model to the Government.
Shearer: Why was it halved? And why wasn’t it 30 percent, or 40 percent, or 70 percent? What was the rationale for half?
Walker: Because we considered that at that level of a half, the agreement would at least—we saw the agreement coming out, that it would be at least delivering to that level, if not beyond.
Shearer: On what basis?
Walker: On the basis of how we could assess the outcomes across the agreement against how we saw the modellers’ thinking of those non-tariff barriers.
No doubt there are economic benefits to removing "non-tariff barriers," but my sense is that we still have a ways to go with defining non-tariff barriers and measuring the impact of their removal.