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2013年7月19日 星期五

一名經人 - 羅家聰 2013年7月19日

一名經人 - 羅家聰 2013年7月19日

羅家聰:說得清楚說得准不是伯老是葉倫 (2013-07-19 08:38:51)

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聯儲局下任主席的熱門人選之一葉倫,坊間有指對其背景知之不甚詳。其實不然。放兩周大假前,在下曾對其學術背景地氈式起底,不計演說,竟起出其具名著作數十,在公司花足整個下午才全數下載(未計打印時間,當然不敢全印)。還記得近八年前,在下起貝南奇底時僅得文獻約半百,與葉倫相約,可見後者在學界的知名度應不低。

葉倫丈夫是2001年諾貝爾經濟學獎得主阿克洛夫(GeorgeAkerlof),讀經濟者,縱無讀過亦應曾聽聞其檸檬市場(the marketfor lemons),為信息不對稱的始祖之一。夫婦二人雖然偶有合著,但葉倫的研究領域卻稍異於其夫。她在1970年代出道初期,主要研究因素市場(factormarket)、賣方壟斷(monopoly)及買方壟斷(monopsony)等微觀經濟,1980年代初轉研技術轉移(technologytransfer);1980年代中兵分三路:漸近理性(nearrational)模型、貿易赤字(tradedeficit)及勞工市場(labourmarket),當中只有勞工市場這瓣一直維持至1996年中,無怪世人對葉倫的印象就是勞工專家。

1997年初,她獲克林頓起用為白宮經濟顧問委員會主席,盡管任期僅至1999年,但在1997至2003年間,葉倫基本上是學術真空,既無署名文章,亦無發表講話。直至2004年中她上任舊金山聯儲銀行主席起,才見她重出江湖著書立說。在過去十年間,她當然是講多過寫了,而範圍亦圍繞經濟展望及貨幣政策,縱在2008年起也談樓市。她以聯儲局身分關於貨幣政策的演說,由2010年初至今三年半;今文要回顧的,是其2012、13年近年半的談話。既是舊說,焦點自然不在貼士風聲,而在其理念政策觀。

露出鴿轉鷹口風
最近而相關的一篇在今年4月發表,題為「PanelDiscussion on "Monetary Policy: Many Targets, Many Instruments.Where Do We Stand?"」。葉倫雖向來被視為「大鴿友」,但這次演說多少已露出其鴿轉鷹的口風,臨尾時指:雖無足夠證據顯示信貸快速增長、顯著杠杆化或重大資產泡沫會威脅金融穩定,但有跡象有人好息(reaching foryield)。此話難譯,但曰「好息之徒」應該無人不明,算是較傳神的譯法吧。此話說在4月中,話口未完半個月,整條債息曲線始急抽,直至近期。要降好息意欲,上策就是加息。

較早前的4月初,另篇演說題為「Communication in Monetary Policy」。政策溝通,是葉倫近兩年講得最多的題材,因貝南奇對此重視,亦著其率領FOMC的溝通小組。只要多讀她的演說,即見在溝通達意上她勝任的。相比其上司貝南奇,雖也主張透明,但礙於其性格內向、怕醜,且近年他已練成「說了很多話而市場無反應」的最高境界;反之葉倫不會如斯詞不達意。譬如這演說中,她指Withunemployment so far from its longer-run normal level, I believe…unemployment should take center stage for the FOMC, even if…inflation slightly and temporarily exceeding 2 percent.此話已見對就業之重視。

又譬如說:I look forward tothe day when we can put away our unconventional tools and return towhat now seems like the relatively straightforward challenge ofsetting the federal funds rate. 配合上文,不難得知當失業問題不再「不正常」,便會退市以至加息。問題是,幾時呢?她說:there willlikely be a substantial period after asset purchases conclude butbefore the FOMC starts removing accommodation by reducing assetholdings or raising the federal funds rate. 類似的說話雖也曾出自貝南奇口,但葉倫顯然清晰得多。

在再較早前、3月初題為「ChallengesConfronting Monetary Policy」的演說當中,清楚點明現在「不正常」的兩個原因:there hasbeen an unusually large and persistent shortfall in aggregatedemand. Second, use of the federal funds rate has been constrainedby the effective lower bound。所以,I"ve……argued that, in such circumstances, optimal policy prescriptionsfor the federal funds rate"s path diverge notably from those ofstandard rules. 這所謂的standard rules,就是敝欄多年前首於中文報章介紹的Taylorrule及其變異版。

相信失業是周期性
那末,失業怎樣才算正常?她參考的指標也很清楚:I therefore expectto consider additional labor market indicators… for example, thepace of payroll employment growth…… In addition, I am likely tosupplement the data on employment and unemployment with measures ofgross job flows, such as job loss and hiring…… I also intend toconsider my forecast of the overall pace of spending and growth inthe economy. 這些,其實都見改善。

在2月題為「A PainfullySlow Recovery for America"s Workers: Causes, Implications, and theFederal Reserve"s Response」的演說中:I cannotspeak for the Committee or my colleagues… However, I see… theincrease in unemployment…… has been largely cyclical and notstructural. 失業若是結構性,貨幣政策無用;相信失業是周期性的,即信政策有用,但潛台詞是政策也是周期性的,不無止境。至於對失業率6.5%、通脹2.5%收水條件,其說法是When one ofthese thresholds is crossed, action is possible but notassured. 幾白?!

上文提到,不正常下不用standardrules。在去年11月題為「Revolutionand Evolution in Central Bank Communications」的演說中,她以坊間市場預期、一般常用的Taylorrule及聯儲局FRB/USmodel算出的optimalrule,來回顧假使不用optimalrule結果如何。如圖所見,沿用optimalrule的失業率跌得較快,但通脹稍逾2%,而零息期將延至整個2015年【圖1,藍線】。但若以Taylorrule或市場預期模擬計,失業率沒跌得這麼快,通脹亦沒那麼高,且2015年中開始加息。可見在這不正常期,葉倫不buy Taylorrule。

若見她容許通脹高於2%目標就卷標是大鴿派,似乎有點曲解了通脹目標了。她指:2 percentcannot be viewed as a ceiling for inflation because that wouldresult in deviations that are more frequently below 2 percent thanabove and thus not properly balanced with the goal of maximumemployment. 她補充:To derive a path【圖1,藍線】……, I assumethat monetary policy aims to minimize the deviations of inflationfrom 2 percent and the deviations of the unemployment rate from 6percent, with equal weight on both objectives.

通脹與失業率占相等權重得出的optimalrule,顯然異於通脹占較重的Taylorrule。正常時期的Taylorrule確實甚能反映儲局政策,但葉倫認為現在是反常期:To be sure,I would never advocate turning over monetary policy to a computer.Now, however, the federal funds rate may well diverge for a numberof years from the prescriptions of simple rules.但何謂number of years?她指:Beyond 2015,the federal funds rate is assumed to gradually rise to 4 percent,……I have assumed…… this process is largely completed within fouryears.

失業率「目標」6%、2015年加息、至4%正常水平、需時四年等等這些具體數字,閣下幾何曾從貝南奇的演說聽過?葉倫就夠膽講了。還有,去年12月起的會後聲明,將維持超低息至何時改為取決於通脹、失業率,其實這早在11月中的演說中已有透露:the Committee might eliminate the calendar date entirelyand replace it with guidance on the economic conditions that wouldneed to prevail before liftoff of the federal funds rate… and I amalso strongly supportive. 只不過她補充,liftoff would notbe automatic once a threshold is reached; that decision wouldrequire further Committee deliberation and judgment.

三個原因看淡前景
在再早即去年6月題為「Perspectiveson Monetary Policy」的演說中,葉倫模擬了Taylorrule與balanced-approach rule,分別是JohnTaylor於1993年的原裝版本及1999年的改良版本。換言之,這里balanced-approach rule對應【圖1】的modifiedTaylor rule。即是說,這次演說還模擬了原裝Taylorrule的結果,當然,是更下策【圖2,紅線】。

這演說時,葉倫對前景看得頗淡,提到三個原因:一有樓市仍差,二有財政懸崖,三有外圍不振。如今回望,第一的樓市已見明顯好轉,第二的財政懸崖已消失於無形,第三的歐、日等外圍最壞日子已過,葉倫回望自己一年前的說法,現鴿轉鷹亦不奇怪。

誠然她當時並非無留腳注的,在去年4月題為「The EconomicOutlook and Monetary Policy」的演說中曾提到:Because anyeconomic forecast is inherently uncertain, the FOMC"s forwardpolicy guidance states explicitly that the Committee "currentlyanticipates" that economic conditions are likely to warrant such astance of policy. The guidance does not state that the Committeewill keep the funds rate exceptionally low until at least late2014. I"d consider it completely appropriate to modify thespecification of the forward guidance in response to significantchanges in the economic outlook. 見嗎?超低息期從未「講死」過。

還有,As I noted, …… GDP has been rising significantlyfaster than now estimated. Alternatively, the economy"s productivepotential could be less than I judge, in which case inflationarypressures could emerge sooner than I expect. 看罷此說,即使回到一年前看,她似乎並非如市場所唱般鴿;而所謂的超低息承諾,亦非如坊間所想般「一成不變」。

觀乎聯儲局副主席說得如斯清楚、具體,相較正主席本周兩次「說了等於沒說」,實在相映成趣。敝欄將繼續介紹葉倫。







一名經人 - 羅家聰 舊文