The point being discussed is that fighting inflation is very much part of the problem.
When the central bank rates hit 0% they can regain traction only by creating and maintaining inflation expectations. Simply expanding the monetary base is like pushing on a string.
The Fed wants to cut the real cost of borrowing. Usually they do this by cutting rates.
But with rates at zero they are powerless.
The real cost of borrowing is interest rate minus inflation. So they can cut rates further, in effect, by creating inflation
and keeping the Fed rate at 0%.
The Krugman paper that Bernanke (once) agreed with is very cool.
At this point matters become difficult. The size of Japan's output gap is, as we have seen,
highly uncertain, although it is probably well over 5 percent. Worse yet, there is no consensus on
the stimulative effect of a given interest rate reduction. As in earlier discussions, it may be useful
to look not at the small number of estimates for Japan, but at the larger range of estimates for that
other large, relatively closed advanced economy, the United States. Table 8 shows estimates of
the reduction in long-term interest rates needed to expand real US GDP by 1 percent.
Given these uncertainties, any number is a matter of multiplicative guesswork.
At this point I
would suggest the following series of leaps of faith: although Japan's current output gap is
probably well over 5 percent, the combination of fiscal stimulus and - if all goes well - a
clarification of which banks will be taken over and which will not should reduce that gap by
several percentage points. So managed inflation would need to close a remaining gap of, say, 4-5
points. Given the median estimate in Table 8, this would require an inflation target of 3-3.75
48 percent. So to give a bit of extra room (one can always raise nominal interest rates if the economy
seems to be overheating - as long as the inflation target is met), how about 4 percent inflation for
15 years?
http://web.mit.edu/krugman/www/bpea_jp.pdf