????或許本?伯南克只能選擇讓影子銀行體系膨脹，才能終止對(duì)債券市場(chǎng)的操縱,。至少,，有些人是這么認(rèn)為的。

????幾個(gè)月來(lái),，美聯(lián)儲(chǔ)（Federal Reserve）內(nèi)外均有傳言稱,，這家美國(guó)央行可能只能采用非常規(guī)方式來(lái)退出債券購(gòu)買計(jì)劃。現(xiàn)在可能有更準(zhǔn)確的說(shuō)法了,。周一,，在伯南克宣布將延后退出刺激計(jì)劃（即所謂的“逐步縮減”）四天后，紐約聯(lián)邦儲(chǔ)備銀行行長(zhǎng)威廉?杜德利表示,，美聯(lián)儲(chǔ)正在測(cè)試通過(guò)所謂的“逆回購(gòu)”方式來(lái)實(shí)現(xiàn)利率逐步上調(diào),。

????美聯(lián)儲(chǔ)在逆回購(gòu)過(guò)程中是從經(jīng)濟(jì)體系中抽取資金：銀行、貨幣市場(chǎng)基金和其他參與者為美聯(lián)儲(chǔ)提供隔夜資金,，獲得收益,。它有點(diǎn)像貸款，但不完全是,。美聯(lián)儲(chǔ)把美國(guó)國(guó)債作為擔(dān)保品給銀行,。回購(gòu)利率事實(shí)上能確定短期利率,，因?yàn)闆](méi)人會(huì)愿意按低于美聯(lián)儲(chǔ)所愿意支付的無(wú)風(fēng)險(xiǎn)利率來(lái)提供貸款,。

????這不是美聯(lián)儲(chǔ)通常上調(diào)利率的方式。過(guò)去它總是通過(guò)出售國(guó)債來(lái)推高利率,。但在美聯(lián)儲(chǔ)持有的美國(guó)國(guó)債和抵押債超過(guò)3.5萬(wàn)億美元后,，這招已經(jīng)不管用了。需要比通常出售更多的債券才能影響市場(chǎng)。而且,，為了安撫市場(chǎng)對(duì)于美聯(lián)儲(chǔ)債券購(gòu)買計(jì)劃的擔(dān)憂,，伯南克基本上已承諾美聯(lián)儲(chǔ)實(shí)際上絕不會(huì)出售這些債券。

????杜德利強(qiáng)調(diào)稱,，這只是一項(xiàng)測(cè)試,。但美聯(lián)儲(chǔ)的債券購(gòu)買計(jì)劃實(shí)施時(shí)間越長(zhǎng)，就越可能最終只能實(shí)施逆回購(gòu)或類似的方式,。

????美聯(lián)儲(chǔ)提出逆回購(gòu)計(jì)劃同時(shí),，美聯(lián)儲(chǔ)很多理事都在討論是否需要遏制回購(gòu)市場(chǎng)和影子銀行體系的其他領(lǐng)域,?；刭?gòu)?fù)ǔ１灰暈橛白鱼y行體系的一部分，因?yàn)檫@些貸款的期限太短,，一般不會(huì)計(jì)入銀行體系的總體杠桿指標(biāo),。而且，很多回購(gòu)是由貨幣市場(chǎng)基金進(jìn)行的,，它們從技術(shù)上講并不是銀行,。就在上周，美聯(lián)儲(chǔ)理事丹尼爾?塔魯洛表示,，監(jiān)管機(jī)構(gòu)應(yīng)當(dāng)把重點(diǎn)放在打擊短期融資市場(chǎng)上,。

????銀行咨詢?nèi)耸坎?伊利說(shuō)：“具有諷刺意味的是，在他們考慮采取逆回購(gòu)方式的同時(shí),，很多美聯(lián)儲(chǔ)人士表示了對(duì)回購(gòu)市場(chǎng)的擔(dān)憂,。”

????但塔魯洛主要擔(dān)心的是銀行使用回購(gòu)市場(chǎng)獲得短期資金,，然后用于長(zhǎng)期高風(fēng)險(xiǎn)資產(chǎn),。很多人相信，使用短期融資導(dǎo)致金融危機(jī)進(jìn)一步惡化,。

????起初,，美聯(lián)儲(chǔ)的計(jì)劃不會(huì)造成這種情況。銀行和貨幣市場(chǎng)基金將給美聯(lián)儲(chǔ)提供貸款,。但美聯(lián)儲(chǔ)的計(jì)劃是從回購(gòu)市場(chǎng)抽回大量資金,。而這些資金不太可能在美聯(lián)儲(chǔ)計(jì)劃結(jié)束后離場(chǎng)，至少不會(huì)立即離場(chǎng),。接下來(lái)可能利用這些短期資金的就是銀行,。

????Ben Bernanke may have to pump up the shadow banking system in order to stop manipulating the bond market. At least that's how some see it.

????For months, there has been talk inside and outside the Federal Reserve that the U.S. central bank might have to use an unorthodox method to exit its bond buying program. That could be even more accurate now. On Monday, four days after Bernanke announced the Fed would put off winding down the program -- the so-called taper -- New York Fed president William Dudley said the U.S. central bank was testing so-called reverse repos as one method to eventually increase interest rates.

????In reverse repos, the Fed drains money from the economy by having banks, money market funds, and others give it money overnight for a fee. It's kind of like a loan, but not quite. The Fed gives banks Treasury bonds as collateral. The rate on the repo effectively sets short-term interest rates, because why would anyone make a loan for less when the Fed is willing to pay risk-free?

????That's not how the Fed typically raises interest rates. Historically, it has sold Treasury bonds to drive up rates. But that may no longer work because the U.S. central bank now has over $3.5 trillion in Treasury and mortgage bonds. It would take much more selling than usual to move the market. What's more, to calm market fears about its bond buying program, Bernanke essentially pledged that the U.S. central bank would never actually sell the bonds.

????Dudley stressed it was just a test. But the longer the Fed's bond buying goes on, the more likely the Fed will eventually have to deploy reverse repos or something like it.

????The reverse repo plan comes at a time when a number of Fed governors have talked about the need to rein in the repo market and other areas of the shadow banking system. Repos are generally considered part of the shadow banking system because the loans are so short that they generally don't get recorded in overall leverage measures of the banking system. What's more, a lot of repos are made by money market funds, which are technically not banks. Just last week, Fed governor Daniel Tarullo said regulators should focus on cracking down on short-term funding markets.

????"It's ironic that they would do this at a time when a number of people in the Fed had said they are worried about repos," says Burt Ely, a bank consultant.

????Tarullo, however, is chiefly worried about banks using the repo market to get short-term loans to fund longer-term riskier assets. Many believe the use of short-term funding made the financial crisis worse.

????Initially, the Fed's plan wouldn't do that. Banks, along with money market funds, would be making loans to the Fed. But the Fed's program is bound to draw a lot of money to the repo market. And that money is unlikely to leave after the Fed program is over, at least not immediately. The next likely user of those short-term funds: banks.