????上周，華爾街牛市邁過了多個重要的里程碑：標準普爾500指數的收盤點位達到了2009年熊市低點的兩倍；羅素2000小型股指數收盤創下歷史新高，收復了2008-2009年熊市的所有失地；以科技股為主的納斯達克綜合指數也漲至十年來的高點。

????人們很容易將這輪反彈歸功于一系列令人鼓舞的經濟數據。但真正的原因可能更多是因為投資者對于現金投資幾乎零回報的不滿情緒。

????沒錯，上周三美國股市出現反彈之時，恰逢有報道稱，歐洲央行（European Central Bank）為了避免讓負債累累的歐洲國家陷入信貸緊縮，將為這些國家的銀行提供超低利率貸款。與此同時，美國商務部（Commerce Department）也宣布，美國經濟增速快于2011年底時的最初預期。而且，美國勞工部（U.S. Labor Department）上上周公布，美國申請失業救濟人數的四周均值已降至四年來的最低。

????這些因素可能是推動投資者加速進入股市的潤滑劑。但此輪股市上漲之時，也正是投資者苦于沒有好的投資渠道之時。正如韋斯特伍德控股集團（Westwood Holdings Group）的首席投資官馬克?弗里曼所說，借貸成本已降至前所未有的低位。事實上，追逐安全投資意味著如今投資者借錢給政府還得倒貼利息。

????過去五年，美國政府支付的平均債券利率逐年下降，已從2006年底的4.92%降至2011年底的2.24%。今年以來，利率進一步下降。弗里曼說，由于通脹率在2%左右，現金的實際回報率已處于負值。

????他對這波股市反彈行情的看法是：“發生變化的是信心在某種程度上的提升，”他說。“投資者現在都說，‘我的現金回報率還是負值，但情況似乎有一點點好轉了。因此，我可能會投資一些風險較高的產品。’”

????美聯儲（Federal Reserve）在啟動之前的兩輪國債購買行動時，大致也是這么想的——最近一次是去年9月的“扭曲操作”，通過推低長期利率，帶來低成本的寬松資金。韋斯特伍德2月份的一份研究報告指出，隨著美國大公司手頭的現金堆積，派息再次開始增加。標普500家的總派息已從2009年的1,960億美元增至2011年的2,410億美元。2012年，預計派息將達到創紀錄的2,750億美元。

????誠然，美聯儲的寬松貨幣政策就算談不上穩定股市，也至少幫助支撐了市場。但未來股市要繼續反彈，難度會更大。迄今為止，還沒有任何跡象顯示美聯儲會啟動新一輪國債購買行動。蛋糕缺少了糖霜、只有基礎配料（也就是美國經濟的基本面轉強），看上去光禿禿的。

????Wall Street's bull market reached a few milestones this week: The S&P 500 index closed at double its bear market low from 2009. The Russell 2000 small-stock index closed at a new all-time high, erasing all of its 2008-2009 bear-market losses. And the tech-dominated Nasdaq composite index rose to its highest point in a decade.

????It's easy to attribute the rally to the slew of cheery economic data. But what's really driving the bulls has more to do with investors frustrated with virtually zero returns on cash.

????True, the market rallied Wednesday amid news that the European Central Bank – in efforts to keep debt-troubled Europe from slipping into a credit crunch – would offer banks ultra-low interest loans. Stocks also rose as the Commerce Department reported that the U.S. economy grew faster than originally thought at the end of 2011. What's more, the U.S. Labor Department reported last week that the four-week average of applications for Americans seeking unemployment aid fell to its lowest point in four years.

????Such factors might be the grease on the wheels driving investors into stocks. However, the gains also come as investors find themselves with few places to get decent returns. As Mark Freeman, chief investment officer of Westwood Holdings Group (WHG), points out, the cost of borrowing is as low as it has ever been. Effectively, the flight to safety means investors are paying to lend money to the government.

????For each of the past five years, the average rates that the government pays on in its debt have declined -- from 4.92% at the end of 2006 to 2.24% at the end of 2011. Rates have fallen further so far this year. With inflation running around 2%, that puts real returns on cash in negative territory, Freeman says.

????He sees the stock rally this way: "What has changed at the margin is that confidence has improved some," he says. "Investors are now saying, 'Hey, I am still getting negative returns on cash and things seem to be doing a little bit better. So maybe I'll invest in something riskier."

????And that's generally what the Federal Reserve had in mind when it launched two rounds of bond purchases – the latest in September under what's called "Operation Twist," which promised cheap and easy money by driving down long-term interest rates. In a February research note, Westwood noted that dividends are beginning to grow again as cash at the biggest corporations piles up. Total dividends paid out by S&P 500 companies rose from $196 billion in 2009 to $241 billion in 2011. In 2012, dividends are expected to be a record $275 billion.

????Indeed, the Fed's easy money policy has helped prop up, if not stabilize, the market thus far. But it's going to be tougher for the stock market rally to continue. So far, the Fed has not signaled any signs it will launch another round of bond purchases. Without the sweet icing – if you will – the cake is left bare with only its basic ingredients. That is, the fundamental strengths of the economy.