国前职业棒球手贝拉（Yogi Berra） 曾说，“棒球有90%是在玩心理战”，那么至少在这一点上，通胀和通缩就与棒球运动非常相似。
美联储除了要关注实际通胀变化率之外，还须密切监视价格走向预期，因为人们的预期经常会自我实现。
美联储周二将召开会议，当下的危险是普遍存在的通货紧缩心态。上周五公布的美国就业数据显示，私营部门仅增加了71000个职位，后继乏力的就业状况更增添了人们的忧虑情绪。
本周会议有可能将进一步讨论美联储是否应大举推出新的刺激经济增长的措施，诸如利用国债到期赚取的资金继续购买国债或抵押贷款支持债券。
美联储不太可能在本周内被迫采取行动。但是市场上越来越多的人相信，它很有可能将会实施所谓“量化宽松”的第二轮措施。
第一轮措施就是通过购买1.7万亿美元的债务制止了房地产市场高台跳水式的暴跌，然而继续实施类似措施是有风险的。
风险之一就是谈论更多的宽松政策会至少在某些情况下造成行业自身的通缩压力。
其 中可能产生这种压力的一个行业就是房地产市场。房地美公司（Freddie Mac）数据显示，30年期房屋抵押贷款平均利率上周跌至4.49%，成为自上世纪50年代以来的最低点。如果现在讨论美联储实施更多宽松政策可能使寻求 房屋贷款再融资的业主或潜在购房者期望贷款利率进一步降低。
如果真是这样，他们可能就会持观望态度，以期更加有利的交易。这是典型的通缩思维。在房地产市场，由于购房者希望在贷款利率升高之前买房，所以一般会加快房屋销售的是利率上涨而非下跌的预期。
低迷的房价再加上超低的房贷利率并不能重振房地产市场，尤其当购房者税收抵免优惠于四月到期以后。六月现房待完成销量同比下跌18.6%。
这正表明，即使对于美联储而言，实施更多的宽松政策也并不一定就如想象般能使日子好过一些。
Inflation and deflation are a lot like baseball, at least considering Yogi Berra's saying that '90% of the game is half mental.'
Besides keeping watch on the actual rate of inflationary change, the Federal Reserve must closely monitor expectations about the direction of prices. That is because those views often become self-fulfilling prophecies.
With the Fed meeting Tuesday, the danger at the moment is that a deflationary mind-set is taking hold. Friday's employment report, which showed anemic gains of just 71,000 private-sector jobs, only adds to such worries.
This week's meeting is likely to feature further debate over whether the Fed should renew extraordinary measures to kick-start growth. These may include resuming purchases of Treasury debt or mortgage-backed bonds, likely, at least to start with, by using money generated from existing holdings of such debt as they mature.
It is unlikely the Fed will feel compelled to act this week. But there is a growing belief in markets that a second round of so-called quantitative easing is likely at some point.
While the first round, via $1.7 trillion of debt purchases, helped arrest the housing-market nose-dive, additional measures carry risks.
One is that talk of more easing creates, at least in some cases, deflationary pressure of its own.
One place this can occur is in housing. Average rates for a 30-year mortgage fell last week to 4.49%, according to Freddie Mac, the lowest rate since the 1950s. Now, talk of more Fed easing may stoke expectations of even lower rates among homeowners looking to refinance, or potential home buyers.
If so, that could cause them to hold off in hope of getting even better deals. That is classic deflationary thinking. And in housing markets, the prospect of rising rates, not falling ones, has typically speeded sales as buyers look to buy before mortgage costs increase.
As it is, already-low home prices coupled with low rates haven't done much to revive housing, especially following the expiration in April of the home buyer's tax credit. In June, pending sales of existing homes fell 18.6% from a year earlier.
It just goes to show that, even for the Fed, doing more isn't always as easy some would think.