Econometric testing

The econometric evidence for NTT was mixed, and again; highly technical. Due to the time-scales required and the particular nature of production in each 'monopolizable' sector, statistical judgements have been hard to make. In many ways, there is too limited a dataset to produce a reliable test of the hypothesis which doesn't require arbitrary judgements from the researchers.

Japan is cited as evidence of the benefits of "intelligent" protectionism, but critics of NTT have argued that the empirical support post-war Japan offers for beneficial protectionism is unusual, and that the NTT argument is based on a selective sample of historical cases. Although many examples (like Japanese cars) can be cited where a 'protected' industry subsequently grew to world status, regressions on the outcomes of such "industrial policies" (including the failures) have been less conclusive.