I must therefore concede that his model is not subject to the sorts of problems I suggested. Anything that has any real effect on human welfare should show up as economic growth, and I don't see any reason to contest his conclusion about the conditions a technology must meet to cause economic growth. Whether nanotechnology can actually meet those conditions is a complex question best addressed elsewhere. So, that reduces most of my comments to a complaint about the inaccuracy of current measurement methods, which isn't especially relevant to the paper. That being the case, I think that it is time for me to retire from the field.
Economists are well aware of the problems with government statistics.
Privately produced estimates can and do include squishy estimates, but their quality is limited by the fact that much less money goes into producing private estimates. You are welcome to submit your comments on the target paper.