Personally I think blood sports are pornographic. Krugman is a persistent pessimist on the future track of US growth. Nick Rowe (the boat) is dipping his oar formally on the optimistic edge of the ram. But surprisingly for apparently Keynesian reasons. Me I am going to err on the side of Krugman’s pessimism because I do not think individuals think like this nor do I think they are homogeneous like this:
Since the actual natural rate has not changed, and since the market rate set by the Fed has not changed, you might think that no individual will want to change his desired savings or investment. But, because each individual (falsely) thinks that the natural rate has increased, relative to the market rate, each individual thinks that every other individual will increase desired investment and reduce desired saving. So each individual expects the Wicksellian/Keynesian cumulative process will cause rising prices and output. And this is what causes each individual to increase his own desired investment and reduce his own desired saving. And so there is a Wicksellian/Keynesian cumulative process of rising prices and output.
Keynesian or not.