Krugman vs. DeLong

Krugman vs. DeLong has an outcome that follows DeLong's rule:

Krugman: The Inflationista Puzzle: Martin Feldstein has a new column on what he calls the “inflation puzzle” — the failure of inflation to soar despite the Fed’s large asset purchases, which led to a very large rise in the monetary base. As Tony Yates points out, however, there’s nothing puzzling at all about what happened; it’s exactly what you should expect when interest rates are near zero.

And this isn’t an ex-post rationale, it’s what many of us were saying from the beginning. Traditional IS-LM analysis said that the Fed’s policies would have little effect on inflation; so did the translation of that analysis into a stripped-down New Keynesian framework that I did back in 1998, starting the modern liquidity-trap literature. ...

DeLong: New Economic Thinking, Hicks-Hansen-Wicksell Macro, and Blocking the Back Propagation Induction-Unraveling from the Long Run Omega Point: ... Whatever may be going on in the short run must thus be transitory in duration, moderate in their effects, and limited in the distance it can can push the economy away from its proper long run equilibrium. And it certainly cannot keep it there. Not for long.

This is the real critique of Paul Krugman’s “depression economics”. Paul can draw his Hicksian IS-LM diagrams of an economy stuck in a liquidity trap...

He can draw his Wicksellian I=S diagrams of how the zero lower bound forces the market interest rate above the natural interest rate at which planned investment balances savings that would be expected were the economy at full employment...

Paul can show, graphically, that conventional monetary policy is then completely ineffective–swapping two assets that are perfect substitutes for each other. Paul can show, graphically, that expansionary fiscal policy is then immensely powerful and has no downside: it does not generate higher interest rates; it does not crowd out productive private investment; and, because interest rates are zero, it entails no financing burden and thus no required increase in future tax wedges. But all this is constrained and limited by the inescapable and powerful logic of the induction-unraveling propagating itself back through the game tree from the Omega Point that is the long run equilibrium. In the IS-LM diagram, the fact that the long run is out there means that even the contemplation of permanent expansion of the monetary base is rapidly moving the IS curve up and to the right, and thus leading the economy to quickly exist the liquidity trap. In the Wicksellian I=S diagram, the fact that the long run is out there means that even the contemplation of permanent expansion of the monetary base is rapidly moving the I=S curve up so that the zero lower bound will soon no longer constrain the economy away from its full-employment equilibrium.

The “depression economics” equilibrium Paul plots on his graph is a matter for today–a month or two, or a quarter or two, or at most a year or two. ...

Krugman:Backward Induction and Brad DeLong (Wonkish): Brad DeLong is, unusually, unhappy with my analysis in a discussion of the inflationista puzzle — the mystery of why so many economists failed to grasp the implications of a liquidity trap, and still fail to grasp those implications despite 6 years of being wrong. Brad sorta-kinda defends the inflationistas on the basis of backward induction; I find myself somewhat baffled by that defense.

Actually, I find myself baffled both theoretically and empirically. ...

In the end, while the post-2008 slump has gone on much longer than even I expected (thanks in part to terrible fiscal policy), and the downward stickiness of wages and prices has been more marked than I imagined, overall the model those of us who paid attention to Japan deployed has done pretty well — and it’s kind of shocking how few of those who got everything wrong are willing to learn from their failure and our success.

DeLong: Paul Krugman Was Right. I, Ken Rogoff, Marty Feldstein, and Many, Many Others Were Wrong: The question is: Why were we wrong? We had, after all, read, learned, and taught the same Hicks-Hansen-Wicksell-Metzler-Tobin macro that was Paul Krugman’s foundation. ...

I want to highlight one of Brad's points. Theoretical models often act as if there is only one type of demand shock, and the short-run depends upon a single variable, e.g. the time period when inflation expectations are wrong. But the short-run depends upon the type of recession we experience, and the variable that signals the length of the recovery will not be the same in every case. A monetary induced recession will have a much shorter short-run than a balance sheet recession induced by a financial collapse, and an recession caused by an oil price shock will recover differently from both. Early in the Great Recession, policymakers, analysts, and most economists did not fully recognize that this recession truly was different, and hence required a different policy approach from the recessions in recent memory. Krugman, due to his work on Japan, did see this early on, but it took time for the notion of a balance sheet recession to take hold, and we never fully adopted fiscal policy to deal with this fact (e.g. sufficient help with rebuilding household balance sheets). To me this in one of the big lessons of the Great Recession -- we must figure out the type of recession we are experiencing, realize that the "short-run" will depend critically on the type of shock causing the recession, and adopt our policies accordingly. If we can do that, then maybe the short-run won't be a decade long the next time we have a balance sheet recession. And there will be a next time.