David Andolfattoが失業率とインフレの関係について論じたエントリに、クルーグマンが、インフレが失業率と無関係に貨幣の需給だけで決まると主張している、と噛み付いた。それに対しAndolfattoが、そうではない、フィリップス曲線の話と貨幣の需給の話は相補的なものだというのが本意だ、と反論している

Oh, dear. We’ve been here before.
Look, economics is about what people (and businesses – corporations are people, my friends) do. Whatever you think is the ultimate cause of an economic phenomenon, your story about how that phenomenon happens has to include an explanation of how peoples’ incentives change. That’s why the doctrine of immaculate transfer, which asserts that saving-investment balances translate into trade balances without any adjustment of the exchange rate, is silly: producers and consumers don’t know or care about S-I, they need to be induced to change their behavior, which requires a change in relative prices.
Similarly, even if you think that inflation is fundamentally a monetary phenomenon (which you shouldn’t, as I’ll explain in a minute), wage- and price-setters don’t care about money demand; they care about their own ability or lack thereof to charge more, which has to – has to – involve the amount of slack in the economy. As Karl Smith pointed out a decade ago, the doctrine of immaculate inflation, in which money translates directly into inflation – a doctrine that was invoked to predict inflationary consequences from Fed easing despite a depressed economy – makes no sense.
And to get back to my broader point: economics is about what people do, and stories about macrobehavior should always include an explanation of the micromotives that make people change what they do. This isn’t the same thing as saying that we must have “microfoundations” in the sense that everyone is maximizing; often people don’t, and a lot of sensible economics involves just accepting some limits to maximization. But incentives and motives are still key.
And it’s ironic that macroeconomists who are deeply committed to the microfoundations project – or, as Trump might say, the “failing microfoundations project” – also seem to be especially likely, perhaps due to their addiction to mathiness, to forget this essential rule.



  1. FRBは失業率がどこまで下がるか知っているのか?
  2. インフレは未だ低いが、それでもFRBは今引き締めるべきなのか?
  3. 失業率とインフレは何か関係があるのか?


This is legitimately debatable--and the FOMC is presently debating it. My own view, on balance, seems presently more aligned with the "doves" on the committee. And so I also agree with Krugman on this score, namely, that the Fed could be tightening too aggressively. Krugman suggests that there are several reasons supporting his view and he mentions a few of them. They are all legitimate reasons, in my view. But I could add more reasons, based on my own preferred theory of inflation. The demand for money (broadly defined to include U.S. treasuries) appears to remain elevated. This disinflationary force has been in place for a long time and could, as I explain here, account for the lowflation phenomenon (see also here). If you follow that link, you'll note that I quote Krugman approvingly in regard to his view about monetary policy in a liquidity trap. Perhaps I am wrong, but I read Krugman here as not recommending that the Japanese lower their unemployment rate to raise inflation. Instead, he appeals to the model I alluded to in my post: a monetary-fiscal theory of inflation. If the Japanese want inflation, just cut taxes and finance social security spending by printing JGBs (as I recommended here). I'm not sure what this has to do with "immaculate" inflation. (I did learn from Nick Rowe that "maculate" is indeed a word.)
これはまともな議論でも意見の分かれるところであり、FOMCでも議論が続いている。私自身の見解は、全体的に言えば、今はFOMCの「ハト派」に近いかと思われる。ということは、この点ではクルーグマンとも意見が同じ、ということである。即ち、FRBは引き締めに積極的過ぎるかもしれない、と考えている。クルーグマンは自分の見解を裏付ける理由は複数あると述べており、そのうちの幾つかに言及している*4。私に言わせればそれらはすべて正当な理由であるが、私のお気に入りのインフレ理論からさらなる理由を付け加えることができる。貨幣(米国債を含む広義の貨幣)への需要は、高まったままのように思われる。このディスインフレ的な力は長期間存在しており、ここで解説したように、低インフレ現象を説明することができる(ここも参照)。リンクを辿れば、流動性の罠における金融政策について私がクルーグマンの見解を肯定的に引用していることに気付くだろう。私が読み間違えているのでなければ、ここ*5クルーグマンが提唱しているのは、インフレを上昇させるために失業率を下げることではない。クルーグマンは、私が記事で触れたモデル、即ちインフレの金融財政理論に訴求している。もし日本がインフレを欲しているのであれば、減税を行って社会保障支出を国債を発行して賄えば良い(それは私がここで推奨したことである*6)。それと「無垢な(immaculate)」インフレがどのように関係しているのかは私には良く分からない(「maculate」という言葉があることはNick Roweに教えて貰ったが)。


I think it would be odd for any macroeconomist schooled in general equilibrium to suggest that the answer to this question is unequivocally no. The answer is yes. The real question is what type of relationship? ...
So perhaps there's some room for debate on point 3. But we should be careful not portray the question as an "either/or" issue. We could just be two blind men, feeling different parts of the elephant--the two interpretations are not necessarily inconsistent with each other. We should try to work this out. On the plus side, it seems we are led to the same policy recommendation. This is something worth noting. (I plead guilty on the score of needlessly antagonizing people who "believe in" the Phillips curve. Rather than suggesting we abandon the theory, I could instead have suggested we supplement it with the monetary view.)
Does the debate over question 3 matter? Yes, it could, because different interpretations of how the world works usually--though not always---implies something different about optimal policy. The Phillips curve theory of inflation suffers from a free parameter problem: the natural rate is unobservable and hence, one can always appeal to a shift in the natural rate to explain away discrepancies with the data. However, the monetary theory I prefer also suffers from a free parameter problem: money demand is not directly observable either. I can always appeal to some unobserved shift in money demand to explain away discrepancies with the data. For this reason, it would be useful for economists to identify "robust" policies--policies that can be expected to deliver good results regardless of which theory best describes the world we are living in.
Is the Phillips curve view of inflation contributing to a policy mistake? I wanted to suggest in my post that it is, although this is not necessarily a fault of the theory as much as how it is applied. That is, there may be no policy mistake in the making if the FOMC simply lets its estimate of the natural rate fall freely as evidence of impending inflation fails to materialize. However, this is not what is happening. As Jim Bullard explained to me, he believes that Phillips curve proponents have a (strictly positive) lower bound on their estimate of the natural rate. The unemployment rate is so low now -- how can it possibly go any lower -- this has to lead to inflation in the near future -- it just has to. We'd better start raising now, before we find ourselves behind the curve.
Here is where the "monetarist" view could temper such resolve. Granted, the global outlook is looking relatively rosy, and fiscal policy seems expansionary--these are both inflation risks from a monetarist perspective. On the other hand, there is considerable uncertainty in this outlook, not the least of which is presently being fueled by talk of a global trade war. In uncertain times, consumers and investors are likely to lower their demand for goods and services--increasing their demand for safe assets, like U.S. dollars and U.S. treasuries. We can see these concerns weigh on long-bond yields. Market-based inflation expectations (like the 5yr-5yr forward) seem well-anchored. Current inflation is running below target. All of this suggests that the Fed can afford not to move aggressively at this time (to be fair, the FOMC regularly emphasizes the "data dependent" nature of its policy path). And yes, this is consistent with PC advocates that are willing to let their estimate of the NRU decline in line with the evidence.
問3を巡る議論は重要だろうか? イエス、重要なものとなり得る。というのは、世界がどのように動いているか、についての異なる解釈は、最適政策についての含意が異なることが多い――常に異なるわけではないが――からである。インフレのフィリップス曲線理論には、自由パラメータ問題がある。即ち、自然失業率は観測不可能であるため、データとの乖離を自然失業率の変化で片付けることが常に可能である。しかし、私の好きな貨幣理論にも自由パラメータ問題がある。貨幣需要というのも直接に観測可能ではないからだ。データとの乖離を観測できない貨幣需要の何らかの変化で片付けることが常に可能である。以上の理由から、「頑健な」政策を識別することが経済学者にとって有用である。それは、我々の住む世界をどの理論が最も良く描写するかとは無関係に、良い結果をもたらすことが期待できる政策である。
インフレのフィリップス曲線的な見解は、政策の過ちに寄与しただろうか? 私の最初の記事で示したかったのは、そうした寄与があった、ということである。ただし、それは必ずしも理論の問題ではなく、その適用の仕方の問題だった。即ち、インフレが差し迫っている証拠が顕在化しないことから、自然失業率の推計値が低下するに任せていれば、FOMCの政策策定の過ちは生じないであろう。だが、実際にはそうなっていない。ジム・ブラードが私に説明してくれたのだが、彼の考えでは、フィリップス曲線の主唱者は、自然失業率の推計に際して(ゼロより大きい)下限を設けている。今や失業率はこれだけ低いのだから――これ以上低くなりようがあろうか――近い将来にインフレが生じるに違いない、それは間違いなく生じる、というわけだ。そこから、手遅れになる前に利上げを今始めよう、ということになる。



*1:cf. ここ

*2:cf. ここ

*3:それで気付いたが、彼は差し障りのありそうなエントリをいつの間にか軒並み削除している(例:本ブログのここここここ[の追記]ここここここここここでリンクしていたエントリ。中には3/16付けのグーグルキャッシュが残っているものもあるので、少なくとも一部はかなり最近削除したらしい)。7年前に別件で炎上騒ぎを経験した後も歯に衣着せぬブログ活動を続けていた彼だが、セントルイス連銀勤めが今年10年目に入ることもあり、かつてタッグを組んでクルーグマンやデロングの悪口を言っていたStephen Williamson(eg. ここ)とは対照的に、大人になったようだ。あるいはWilliamsonが2014年から勤務していたセントルイス連銀を昨年退職したことと考え合わせて下衆の勘繰りをするならば、ブラード総裁辺りから何らかのお達しがあったのかもしれない…。


*5:cf. ここ

*6:cf. ここ