Think outside the box


クルーグマン"It's Baaack"は「誤解だぁっ!」


クルーグマン氏が決定的役割-安倍首相の増税延期の決断で - Bloomberg

Abe Listening to Krugman After Tokyo Limo Ride on Abenomics Fate - Bloomberg

リフレ政策の御本尊・クルーグマンが日本への関心を強めたのは、1998年に"Japan's Trap"で管理インフレを唱えてからです。そこで、その詳細版の"It's Baaack: Japan's Slump and the Return of the Liquidity Trap"について振り返ってみます(下は山形浩生訳)。*1



It's Baaack: Japan's Slump and the Return of the Liquidity Trap 

Indeed, the normal view is that money is roughly neutral: that an increase in the money supply produces a roughly equiproportional increase in the general price level. Or to be more specific, an increase in outside money-the monetary base-must raise prices. 

まさにふつうの見方は、マネーはおおむね中立的だ、というものだ――マネーサプライが増えると、一般価格水準もほぼそれと同じ割合で増大する。あるいはもっと厳密に言えば、外部 (outside) のお金――つまり monetary base――が増えると価格は必ず上がる。

Money (which is to say, outside money) is supposed to be just plain neutral.

マネー(つまりは outside のマネー) は無条件でなにがなんでも中立のはず、なんだ。

an increase in the money supply in the current and all future periods will raise prices in the same proportion.


A monetary expansion that the market expects to be sustained (that is, matched by equiproportional expansions in all future periods) will always work, whatever structural problems the economy might have;







Banks, however, need hold only a fraction π of their deposits in reserves and will hold no more than necessary; they lend the rest out (which is how consumers get the money for the deposits). So bank deposits will be a multiple 1/π of the monetary base; the velocity of base will be 1, that of deposits ,π. And from here on, the model will work in pretty much the same way as the pure outside money model in the text. 

でも銀行は、自分たちの預金のうち π の割合だけをリザーブとして持っておけばよくて、必要以上は現金を持たない。残りは貸し出す(消費者が預金のお金を得るのはここからだ)。だから銀行口座はマネタリーベースの 1/π 倍になる。ベースマネーの速度は 1 になって、預金の速度はπ だ。そしてここから、モデルはおおむね文中の純粋な outside-money モデルとほぼ同じように機能してくる。

預金準備率π=10%の場合、銀行がマネタリーベース1000を入手する→900を貸し出す(100は中央銀行の準備預金に)→借り手が銀行に預けた900のうち810を貸し出す(90は準備預金に)→借り手が銀行に預けた810のうち729を貸し出す(81は準備預金に)→・・・のプロセスが続くと、銀行の預金口座は1000+900+810+729+・・・=10000となります。当初の1000が銀行が'multiply up'した結果10000(=1000/0.1)に増えるという貨幣乗数のメカニズムです。

したがって、「中央銀行が銀行にoutside money(マネタリーベース)を追加供給すると銀行が貸し出せる資金(loanable funds)が増える→マネーサプライ増加」ということになります。


To understand what’s going on, you have to know a bit about how monetary policy usually operates.

The Fed’s economic power rests on the fact that it’s the only institution with the right to add to the “monetary base”: pieces of green paper bearing portraits of dead presidents, plus deposits that private banks hold at the Fed and can convert into green paper at will.

When the Fed is worried about the state of the economy, it basically responds by printing more of that green paper, and using it to buy bonds from banks. The banks then use the green paper to make more loans, which causes businesses and households to spend more, and the economy expands.*3

2012年には「銀行は'loanable funds'を仲介している」「銀行は無から預金を創造しない」と解説しています。"It's Baaack"は、マネーサプライは根源的には中央銀行が創造・供給している、というモデルに基づいています。

For in the end, banks don’t change the basic notion of interest rates as determined by liquidity preference and loanable funds — yes, both, because the message of IS-LM is that both views, properly understood, are correct. Banks don’t create demand out of thin air any more than anyone does by choosing to spend more; and banks are just one channel linking lenders to borrowers.

クルーグマンが好んで用いる「子守協同組合」 モデルでは、発行体から組合員に直接クーポンが渡ります。現実の経済では中央銀行と企業・家計の間に銀行が存在しますが、単に仲介するだけなので、中央銀行がクーポンを増刷する(=マネタリーベースを増やす)だけで「さっさと不況を終わらせ」ることができる、となるわけです。*4

Baby-Sitting the Economy

This could indeed lead to a slump—but need not if the management were alert and responded by simply issuing more coupons. That is exactly what our head coupon issuer Alan Greenspan did in 1987—and what I believe he would do again. *5


  • Money is created when a bank loans any excess reserves it holds.
  • Bank lending leads to new deposits in the banking system and a multiplier effect on the money supply.


Money creation in the modern economy - Quarterly Bulletin article - YouTube

One common misconception is that banks act simply as intermediaries, lending out the deposits that savers place with them. In this view deposits are typically ‘created’ by the saving decisions of households, and banks then ‘lend out’ those existing deposits to borrowers, for example to companies looking to finance investment or individuals wanting to purchase houses.

In fact, when households choose to save more money in bank accounts, those deposits come simply at the expense of deposits that would have otherwise gone to companies in payment for goods and services. Saving does not by itself increase the deposits or ‘funds available’ for banks to lend*7

Another common misconception is that the central bank determines the quantity of loans and deposits in the economy by controlling the quantity of central bank money — the so-called ‘money multiplier’ approach. In that view, central banks implement monetary policy by choosing a quantity of reserves. And, because there is assumed to be a constant ratio of broad money to base money, these reserves are then ‘multiplied up’ to a much greater change in bank loans and deposits. For the theory to hold, the amount of reserves must be a binding constraint on lending, and the central bank must directly determine the amount of reserves. While the money multiplier theory can be a useful way of introducing money and banking in economic textbooks, it is not an accurate description of how money is created in reality.

This description of money creation contrasts with the notion that banks can only lend out pre-existing money, outlined in the previous section. Bank deposits are simply a record of how much the bank itself owes its customers. So they are a liability of the bank, not an asset that could be lent out. A related misconception is that banks can lend out their reserves. Reserves can only be lent between banks, since consumers do not have access to reserves accounts at the Bank of England.

Money creation in practice differs from some popular misconceptions — banks do not act simply as intermediaries, lending out deposits that savers place with them, and nor do they ‘multiply up’ central bank money to create new loans and deposits.

  • 預金は銀行の負債であって貸し出せる資産ではない
  • 銀行は預金者の預け入れた預金を仲介して貸し出しているのではない
  • 準備預金は企業や家計に貸し出せない
  • 銀行は預金や準備預金を'multiply up'してマネーサプライを増やすのではない

イングランド銀行の金融政策 (世界の中央銀行)

イングランド銀行の金融政策 (世界の中央銀行)


Monetary policy implementation: Misconceptions and their consequences

The central misconception regarding monetary policy implementation is the proposition that monetary policy actions are effected through open market operations that alter some quantity aggregate, such as the monetary base or a reserve aggregate. Such a depiction of monetary policy implementation is prevalent in the academic literature and standard in leading macroeconomic textbooks.

Moreover, in models embedded with a banking sector that plays a non-trivial role, the characterization of monetary policy through the control of money supply implicitly assumes that central bank actions have direct bearing over banks’ supply of loanable funds, and thus on their intermediation activity. This presumes that central banks are more powerful than they really are

This is premised on the notion that central banks set the level of reserves as the operational target of policy and that banks’ deposit base, and thus their supply of loanable funds, is linked directly to variations in reserves through the money multiplier mechanism. In fact, the true causal relationship actually runs in exactly the opposite direction. The banking system creates deposits as they are demanded by the private sector, and the central bank’s main liquidity management task is to ensure a sufficient supply of balances for the system as a whole to maintain reserve requirements, if any, associated with those deposits. It is the amount of deposits that the banking sector can attract that determines the level of reserves not the other way around.



イングランド銀行の説明が正しいとすれば、金融の仕組みの根本的誤解に基づいた"It's Baaack"の結論(日本への政策提言)をどう評価すればよいのでしょうか。

雇用、利子および貨幣の一般理論〈下〉 (岩波文庫)

雇用、利子および貨幣の一般理論〈下〉 (岩波文庫)

経済学者や政治哲学者の思想は、それらが正しい場合も誤っている場合も、通常考えられている以上に強力である。実際、世界を支配しているのはまずこれ以外のものではない。誰の知的影響も受けていないと信じている実務家でさえ、誰かしら過去の経済学者の奴隷であるのが通例である。虚空の声を聞く権力の座の狂人も、数年前のある学者先生から〔自分に見合った〕 狂気を抽き出している。

…, the ideas of economists and political philosophers, both when they are right and when they are wrong, are more powerful than is commonly understood. Indeed the world is ruled by little else. Practical men, who believe themselves to be quite exempt from any intellectual influences, are usually the slaves of some defunct economist. Madmen in authority, who hear voices in the air, are distilling their frenzy from some academic scribbler of a few years back. *9




アメリカ連邦準備制度(FRS)の金融政策 (〔世界の中央銀行〕)

アメリカ連邦準備制度(FRS)の金融政策 (〔世界の中央銀行〕)




  • 雨が降らない→「祈り」が不十分(神に伝わっていない)→より強く祈る
  • 雨が降る→効果が実証された



  • インフレ率が上昇しない→中央銀行のコミットメントとアクションが不十分→追加緩和
  • インフレ率上昇→効果が実証された


The Holy Grail of Macroeconomics: Lessons from Japans Great Recession

The Holy Grail of Macroeconomics: Lessons from Japans Great Recession

Even though quantitative easing failed to produce the expected results, the belief that monetary policy is always effective persists among economists in Japan and elsewhere. To these economists, quantity easing did not fail: it simply was not tried hard enough. According to this view, if boosting the excess reserves of commercial banks to ¥25 trillion has no effect, then we should try injecting ¥50 trillion, or ¥100 trillion.

At the risk of belaboring the obvious, imagine a patient in the hospital who takes a drug prescribed by her doctor, but does not react as the doctor expected, and, more importantly, does not get better. When she reports back to the doctor, he tells her to double the dosage. But this does not help, either. So he orders her to take four times, eight times, and finally a hundred times the original dosage. All to no avail. Under these circumstances, any normal human being would come to the conclusion that the doctor's original diagnosis was wrong, and that the patient suffered from a different disease.






Will Mounting U.S. Debt Spark Inflation? -- Forefront: New Ideas on Economic Policy from the Federal Reserve Bank of Cleveland

Debt monetization implies a permanent increase in the money supply …


The government in Zimbabwe, to cite the most extreme example, recently used money created by its central bank to reduce the value of the nation's nominal deficit—a practice known as monetizing the debt. Money creation grew so rampant in Zimbabwe that at one point inflation skyrocketed to an insane monthly rate of 79 billion percent.



インタビュー:アベノミクス極めて順調、構造改革断行を=浜田参与 | Reuters