昨日紹介したバーナンキ論文「Monetary Policy in a New Era」に関するパネル討論にFRBのブレイナード理事も参加し、事前に用意したコメントで「バーナンキ論文は、この新たな環境の中で金融政策を行うFRBの努力に関して優れた概観を提供し、興味深い新提案を幾つか行っている(Bernanke's paper provides an excellent review of the Federal Reserve's efforts to operate in this new environment and makes some interesting new proposals)」と書いている。その新提案の中で最も注目を集めたのが、インフレ目標と価格水準目標を組み合わせた枠組みの提案である。同提案は本人のブログエントリでも紹介されているが、シンポジウムに出席したCarola Binderが以下のようにまとめている

Ben Bernanke raised probably the most specific and novel policy idea of the conference, a monetary policy framework that would resemble a hybrid of inflation targeting and price level targeting. In normal times, the central bank would have a 2% inflation target. At the zero lower bound, the central bank would allow inflation to rise above the 2% target until inflation over the duration of the ZLB episode averaged 2%. He suggested that this framework would have some of the benefits of a higher inflation target and of price level targeting without some of the associated costs. Inflation would average 2%, so distortions from higher inflation associated with a 4% target would be avoided. The possibly adverse credibility costs of switching to a higher target would also be minimized. The policy would provide the usual benefits of history-dependence associated with price level targeting, without the problems that this poses when there are oil shocks.
It’s an exciting idea, and intuitively really appealing to me. But how should the Fed ever decide whether or not to implement it? Bernanke mentioned that economists at the Board are working on simulations of this policy. I would guess that these simulations involve many of the assumptions and linearizations that rethinking types love to demonize.
これは刺激的なアイディアであり、直観的に私は非常に惹きつけられた。しかしFRBは、これを導入するか否かをどのように決定すべきなのだろうか? バーナンキFRBの経済学者がこの政策のシミュレーションを実施していると述べた。そうしたシミュレーションには、経済学再考が好きな人が敵視するような前提や線形化が数多く使われるものと思われる。

ブレイナードも前記のコメントでこの提案を中心的に取り上げ、早期に正常な状態に戻したいという「正常化バイアス(Normalization Bias)」を回避する手段になる、と述べている。

The proposed temporary price-level targeting policy is designed to address what I see as one of the key challenges facing policymakers. Following deep recessions of the type we experienced in 2008-09, there appears to be an important premium on "normalization." This was apparent in 2010, for instance, when there was substantial pressure among Group of Twenty officials to commit to timelines and targets for reducing fiscal support and to articulate exit principles for monetary policy. This inclination proved premature, as was evident from the subsequent intensification of the euro-area crisis.
Moreover, the benchmark for "normal" tends to be defined in terms of pre-crisis standards that involved policy settings well away from the lower bound, at least initially, because it may take some time to learn about important changes in underlying financial and economic relationships. For example, the factors underlying what we now understand to be the new normal of persistently low interest rates were in many cases initially viewed as temporary headwinds. In these circumstances, a standard policy framework calibrated around the pre-crisis or "old" normal may be biased to underachieving the inflation target in a low neutral rate environment. The kind of policy framework that Bernanke proposes, which pre-commits to implementing the makeup principle based on the actual observed performance of inflation during a lower bound episode, could guard against premature liftoff and help prevent the erosion of longer-term inflation expectations.


Monetary policymakers operate in an environment of considerable uncertainty and therefore have to weigh the risks of tightening too little or too late against those of tightening too much or too soon. While past experience has conditioned U.S. policymakers to be highly attentive to the risks associated with a breakout of inflation to the upside, as in the 1970s, they balance these risks against those associated with undershooting the inflation target persistently, as in Japan in the late 1990s and the 2000s.
In weighing these risks, the standard approach is typically designed to achieve "convergence from below," in which inflation gradually rises to its target. Given the lags in the effects of monetary policy, convergence from below would necessitate raising interest rates preemptively, well in advance of inflation reaching its target. Moreover, particularly in the early stage of a recovery, this kind of preemptive approach tends of necessity to rely on economic relationships derived from pre-crisis observations, when policy rates were comfortably above the lower bound.
During a period when the policy rate is limited by the lower bound, Bernanke's proposal would represent a substantial departure from the standard approach. While a standard policy framework would tend to prescribe that tightening should start preemptively, well before inflation reaches target, Bernanke's temporary price-level target proposal would imply maintaining the policy rate at the lower bound well past the point at which inflation has risen above target. In principle, policymakers would have to be willing to accept elevated rates of above-target inflation for a period following a lengthy period of undershooting.


  • 高インフレを目にした一般が、中銀のインフレ目標への信認に疑問を抱くというリスク
    • 現在は低インフレで逆の疑問が生じているが、インフレのオーバーシュートを許容することには思わぬ行き過ぎの可能性も少なからず存在する。
    • 中銀自身が経済が強い中でゼロ金利を続けることに耐えられなくなるかもしれない。
  • 物価水準目標からインフレ目標に移行する時に引き締めが急なものとなるリスク
    • バーナンキ提案では、累積的なインフレが平均2%になった時点で通常の政策ルールに戻ることになるが、その時にはインフレが目標を上回り経済は完全雇用を超えているので、平滑化(慣性的)特性を考慮に入れたとしても、標準的な政策ルールからは比較的急な引き締め経路が導出されるだろう。そうした政策金利の経路予想が、この枠組みの長所を一部打ち消してしまうかもしれない。
    • そのため、金利引き上げ時には移行期の枠組みが必要になると思われるが、そうするとコミュニケーションと政策がともに幾分複雑化することになる。
  • 他の政策ツールとの兼ね合い
    • 今後、ゼロ金利においては、大規模な資産購入とフォワドガイダンスも政策ツールとして展開されていると想定される。その場合、バランスシートを維持することは、政策金利の引き上げによる経済への影響を一部埋め合わせることになる*1
    • 資産買い入れは政策の枠組みとコミュニケーションを複雑化させる。というのは、その展開と撤収は非連続的であるため、政策反応関数における不確実性が大きくなるためである*2
    • 従って、バーナンキの枠組みでは、影の金利*3といった政策ツールを統合した指標でコミュニケーションを行うのが望ましい。

*1:cf. クリス・ディローの議論


*3:cf. ここここここここ。ブレイナードは参照論文としてこれこれを挙げている。