美元喜欢通胀？

    半年来，批评人士一直在嚷嚷说，伯南克的宽松政策会引发大规模通货膨胀，导致美元贬值。随着美元指数接近52周低点，通胀预期略有上升，抛售美元的论调近日有所升温。

    但是，要是所有这些批评都错了，美联储（Fed）寻求温和通胀并不注定美元就是要贬值？要是事实上经济增长乏力对美元的影响更大呢？

    这很难说，因为外汇交易中有太多因素，从货币政策到贸易流，再到经济增长等等。但显然，仅仅通胀上升并不意味着美元就会下跌。

    回顾过去25年，美元交易的两个阶段——1988年至2001年是美元上涨期，2001年至今是美元下跌期。

    你或许会以为后一个时期的消费者价格指数(CPI)涨幅可能较高。要求伯南克下课的呼声以及对于食品和能源价格上涨的抱怨，当然都指向于此——相反，90年代留给人们的记忆则是通缩型繁荣。

    但美国银行（Bank of America）的经济学家伊桑•哈里斯指出，美元上涨期的CPI平均涨幅为3.2%，而此后为2.4%。所谓的“印刷纸币可能造成不可挽回的影响”的论调，可以休矣。

    “如果(货币发行)从自律到‘贬值化’的转变是在推高通胀，这一影响被其他因素淹没了”，哈里斯写道，“而且，如果批评人士是对的，美联储在加大美元贬值力度，为何过去几年美元走势平稳？”

    当然，部分原因是美元兑其他货币的汇率总是会有涨有跌，而欧元区近年来在金融稳定方面也确实乏善可陈。

    但如果看一看美国的经济增长率（90年代增长强劲，近十年疲弱），你也可以为90年代美元的上涨和过去十年美元的下跌找到合理的解释。即便现在，你也可以说，弱势美元未能充分反映美国的增长潜力，特别是美元/日元汇率——在上周的汇率干预前，日元正在攀向新高。

    “美元并不经常能因为美国经济增长而受到推崇”，MF Global外汇分析师杰西卡•赫文森表示。

    在这样的情况下，尽管欧元区仍存在政治问题和纾困担忧，欧元/美元处于52周高点。欧洲央行（European Central Bank）已表示，预计下个月将上调利率，为高涨的大宗商品价格降温。

    眼看油价即将升至4美元/加仑，狡猾的央行银行家们能有这样的明确表态确属罕见。但回想起2008年欧洲央行应夏季油价大涨而上调利率后的结局，哈里斯表示，批评者在抨击伯南克前最好先回顾一下去年欧洲的情形。

    “对于有些人而言，这证明伯南克在通胀方面是一个超级鸽派，”哈里斯写道，“在我们看来， 这证明他对前景风险的判断优于其批评者。”

    不过，这并不能说明太多问题。

    For six months critics have been screaming that Bernanke's loose policy would set off massive inflation and destroy the value of the dollar. Dump-the-dollar calls have picked up lately, with the dollar index near a 52-week low and inflation expectations rising a bit.

    But what if all the yelling is wrong and the Fed's pursuit of modest inflation doesn't doom the dollar? What if the dollar is actually more allergic to anemic growth?

    It's hard to say for sure because there are so many factors in currency trading, ranging from monetary policy to trade flows to economic growth. Yet it's clear that higher inflation alone doesn't mean a weaker dollar.

    Consider the two dollar trading regimes in the past quarter century: the rising dollar world of 1988-2001, and the falling dollar world since.

    You might assume consumer price inflation has been higher in the latter period. Calls to can Bernanke and complaints about higher food and energy prices certainly suggest this -- as does the memory of the 1990s as a disinflationary boom.

    Yet the CPI averaged 3.2% in the rising-dollar period and 2.4% since, Bank of America economist Ethan Harris says. So much for the supposedly irreversible dangers of printing.

    "If this shift from discipline to 'debasement' is increasing inflation, the impact is being swamped by other developments," Harris writes. "Moreover, if critics are right and the Fed is increasing its debasement of the dollar, why has the dollar leveled off in the last few years?"

    In part, of course, the answer there is that the dollar has to rise and fall against something, and the euro area is not exactly setting any financial stability records lately either.

    But you can also rationalize the dollar's rise during the 1990s and its fall during the past decade by looking first at U.S. growth, which was strong then and has been weak lately. Even now you could argue the dollar's weakness fails to appreciate U.S. growth potential – particularly vis a vis Japan's yen, which was hitting new highs before last week's intervention.

    "The dollar doesn't always get a lot of credit for the growth story here in the U.S.," says MF Global currency analyst Jessica Hoverson.

    To that end the euro, for all its political problems and bailout fears, is trading at a 52-week high against the dollar. The European Central Bank has signaled it expects to start raising interest rates next month, in a bid to cool rising commodity prices.

    In a world where $4 gasoline is coming soon, that sounds like a rare bit of clear-headed resolve from weaselly central bankers. But Harris, recalling what happened when the ECB raised rates in 2008 in response to that summer's oil spike, says detractors would do well to see how this latest inflation-scare movie turns out before bashing Bernanke.

    "For some, this episode is evidence that Bernanke is an über dove on inflation," writes Harris. "To us it is evidence that he is a better judge of the risks around the outlook than his critics."

    Not that that's saying much, really.