I would say that the revision down is primarily structural. I wouldn't quite use the word “permanent”, but that revision reflects four separate methodologies that look at it through different lenses.
The main thing that's going on there is that the global neutral rate appears to have drifted lower and has done so for the last couple of years. That happens in the context of important drivers such as a slowing labour force growth, because those of us who were baby boomers are gradually retiring. That big bulge in labour force participation is a 50-year period during which we had much stronger growth in the labour force globally, not just here. That's coming down to what you might consider to be historically more normal, if you think of the 50 years as abnormal. That is the primary driver and that's just.... Again, it's close to mechanics. It's not a very sophisticated analysis. It's just that you can't have much.... The economic growth trend line for the world is driven by that labour force and by productivity. Only if we did have a long-lasting rise in productivity would there be pressure for it to rise, which is why I wouldn't say “permanent”—because that, of course, is quite possible.