????美聯儲（Federal Reserve）主席本?伯南克經常因為對股市過度反應而遭受批評。不過也許他就該這么干。

????上一次股市大崩盤后，美聯儲推出了第二輪量化寬松和“扭轉操作”。最近道瓊斯指數再次大跌（盡管昨日有所反彈），再加上其它一些比較疲軟的經濟數據，讓人懷疑伯南克和美聯儲是否會再次推出一輪新的刺激計劃。同時，也有些人對伯南克的救市手段感到不滿，認為伯南克更關心的是股市的方向，而不是總體的經濟狀況。還有些人批評伯南克站在了投資者一邊，而不是消費者這邊，認為美聯儲的舉措可能會引發大規模的通脹。

????不過一份最新研究顯示，監視股市的動向也許正是伯南克此時應該做的事情。美國國家經濟研究局（NBER）近日發布了一篇名為《通脹追蹤投資組合》（Inflation Tracking Portfolios）的工作文件，研究了自1985年初一直到去年年末的消費價格以及一系列投資活動的變動。這篇報告的作者包括加州大學洛杉磯分校（UCLA）的經濟學教授弗朗西斯?朗斯達夫，以及投資銀行黑石集團（Blackrock）的兩名雇員。研究發現，大多數被我們當成通脹避險工具的東西，比如黃金和房地產，都有夸大價格實際波動的傾向。就連政府發行的抗通脹公債也不能很好地預言未來的通脹。抗通脹公債價格的波動往往遠遠超過總體消費價格的波動。通脹最好的預言者恰恰就是股市。

????該研究報告的作者們發現，從總體來看，未來的通脹往往會隨著股市的走向而變動，在這一點上，股市預言通脹的能力比他們考察的任何其它因素都強。因此，如果股市接連一個月下跌的話，很可能就意味著一個月后通脹水平會降低。如果股市暴漲，則可能意味著消費價格未來也會上漲。

????此外，該研究報告的作者們還發現，有些行業的通脹敏感性要高于其它行業。比如石油股往往會與通脹呈同向波動，而零售股與通脹的相關性則比較小。所以如果真想追蹤通脹的話，我們需要建立一個投資組合，做多與通脹相關的行業股，做空與通脹不相關的行業股——該研究報告的作者們就是這樣做的。那么，這個通脹組合對眼下有何預測呢？大體來看，通脹水平（5月份已下降0.3%）還會繼續下降。報告的作者們在2011年年底就已經停止了構建那個投資組合。不過上個月石油股下跌了14%。而包括沃爾瑪（Wal-Mart）和塔吉特百貨（Target）在內的一些零售股卻出現了上升。西爾斯百貨（Sears）的股價則出現了下跌。

????朗斯塔夫表示，他并不是想要對政府的貨幣政策發表任何說長道短。不過股票的確是未來通脹的最好的預言師。那么，一旦股市暴跌，伯南克再次像以前一樣出手救市就不難理解了。考慮到五月份的情況有多糟糕，美聯儲說不定正醞釀著另一輪量化寬松或其它的刺激計劃，至少美聯儲應該做好這樣的準備。

????譯者：樸成奎

????Federal Reserve chairman Ben Bernanke often gets criticized for overreacting to the stock market. But maybe that's exactly what he should be doing.

????QE2 and Operation Twist were announced after market drops. And the recent swoon in the Dow, despite rebounding yesterday, along with some rather weak economic data, have reignited new speculation that Bernanke & Co. might finally announce a new stimulus program. That's led some critics to contend that Bernanke cares more about the direction of stocks than the general economy. Others, who predict the Fed's moves will spark massive inflation, say Bernanke is choosing investors over consumers.

????But a new study suggests that keeping an eye on the market is exactly what Bernanke should be doing. Inflation Tracking Portfolios, which was released as a working paper by the NBER this week, looked at the movement in consumer prices and a number of various investments from the beginning of 1985 through the end of last year. The study's authors, which included UCLA economics professor Francis A. Longstaff and two employees from investment firm Blackrock, found that most things that we generally tend to think of as inflation hedges, such as gold and real estate, tend to overstate the actual moves in prices. Even Inflation-Protected Treasury bonds, nicknamed TIPs, came out as a pretty poor predictor of future inflation. Prices of TIPs tended to jump around much more than overall prices did. The best inflation oracle: the market.

????In general, the authors found that future inflation tends to track stocks better than anything else they looked at. So if the market dropped over the course of a month, it tends to indicate that inflation will be lower a month from now. A jump in stocks, tends to mean consumer prices will rise as well.

????What's more, the authors found some industries are more correlated to inflation than others. Oil stocks tend to move in the same direction as inflation; retail stocks, not as much. So if you really want to track inflation, you need to build a portfolio that long the sectors that are correlated with inflation and short the sectors that are not, which is what the authors of the study did. What is the inflation portfolio predicting now? Generally, that inflation, which dropped 0.3% in May, will continue to fall. The authors stopped constructing their portfolio at the end of 2011. But oil stocks are down 14% in the past month. A number of retailing stocks, on the other handing including Wal-Mart (WMT) and Target (TGT) are up. Sears (SHLD) is down.

????Longstaff says he wasn't looking to make any statement about monetary policy. But if stocks are really the best indicator of future inflation, then it seems to make sense that Bernanke would jump to action, as he has, when stocks have dropped. And given how bad May was, another QE or some other round of Fed stimulus is probably on its way, or at least it should be.