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2019年9月4日

徐家健 經濟3.0

美股美股我愛你

幫零售業算算賬,上月我這樣說過:「根據政府最近發表的零售業銷貨額臨時統計數字,2019年5月的零售業總銷貨數量的修訂估計較2018年同月下跌1.8%,而到了政治爭拗開始的6月份相關跌幅擴大至7.6%。再與2018年同期比較,2019年上半年的零售業總銷貨數量的臨時估計下跌3.1%。按零售商主要類別的銷貨價值的臨時估計,2019年6月與2018年6月比較跌幅最大的是珠寶首飾、鐘錶及名貴禮物,銷貨價值大跌17.1%,其次服裝亦下跌8.2%。相反,超級市場貨品的銷貨價值上升了1.6%⋯⋯簡單總結,根據最新公布的統計數字,2019年上半年零售業的嚴峻程度比不上沙士時期或金融風暴,更比不上2016年時大跌市後零售業的經濟困境。

沒有水晶球,2019下半年的零售業會比以往我們面對過的情況更加嚴峻嗎?」

一個月後,政府發表7月份的零售業銷貨額臨時統計數字。一如所料,扣除價格變動後7月的零售業銷貨額較去年同月挫13%,相比6月份7.6%的跌幅擴大了接近一倍。按零售商主要類別的銷貨價值,跌幅最大的繼續是珠寶首飾、鐘錶及名貴禮物,銷貨價值大跌24.4%。其次服裝下降13.0%,亦比上月的相關跌幅大。嚴峻程度是否比得上沙士時期或金融風暴,還要多看一季。然而,即使因修訂《逃反條例》而引發的遊行示威及警民衝突能夠最終平息,中美矛盾並非一年半載可以徹底解決的問題。面對這個外憂內患的境地,短期內不會消失的非慣常周期性逆轉,投資者可以做些什麼?

本土偏見愈演愈烈

現代金融學之中,最重要的一個投資建議可能源自著名的《基金分離定理》(Two-Fund Separation Theorem)有效率的分散投資,是把整個市場的分散投資。然而,金融學上所謂的「本土偏見」(home bias),指的是投資者傾向投資自己地方的資產,對海外資產興趣不大。這偏見有普遍性,絕非香港獨有。

偏見的形成,可以傳統經濟因素所致,如高交易費用、大估計錯誤、非常態分配回報等等。要知道,美股市場佔全球股票市場約一半的比例,美國人有本土偏見是小,香港人有本土偏見是大。我當然明白,全球化之下世界各地的經濟表現變得更為同步,不同市場齊上齊落亦導致本土偏見造成的經濟損失減少。但試想,回歸以來,與香港經濟表現齊上齊落的是美國還是內地呢?

現實是,當中美矛盾愈演愈烈,美股與港股齊上齊落的關係只會愈來愈弱,港人港股的本土偏見亦變得愈來愈嚴重。即使沒有內地經濟硬着陸或港元脫鈎等極端金融危機,投資佔全球股票市場一半的美股市場是需要分散投資的投資者不容忽視的。

分散投資理論與實踐

畢非德對分散投資一向不以為然:

Diversification is protection against ignorance. It makes little sense if you know what you are doing.

股神倡議多年的價值投資法,是精選管理完善而市價被低估的優質股:

"You will notice that our major equity holdings are relatively few. We select such investments on a long-term basis, weighing the same factors as would be involved in the purchase of 100% of an operating business: (1) favorable long-term economic characteristics; (2) competent and honest management; (3) purchase price attractive when measured against the yardstick of value to a private owner; and (4) an industry with which we are familiar and whose long-term business characteristics we feel competent to judge. It is difficult to find investments meeting such a test, and that is one reason for our concentration of holdings."

問題是,我們不是股神,尤其一般香港人對美股的認識十分有限。這個時候,諾獎得主夏普(William Sharpe)一直主張的被動投資,是個值得認真考慮的選擇:

Think about all the securities in a marketplace and think about a strategy of investing proportionally, or broad indexing. If I have 1% of the money in that market, I'll buy 1% of the stocks of every company in the market and I'll buy 1% of the outstanding bonds. So I’ll have a portfolio that truly reflects the marketplace. Then think about all the people engaging in other strategies, active strategies, holding different amounts of this or that. Then you ask at the end of any period - be it a year, a month, you name it - What did the passive investors earn before costs? And let's say that's 12%, just to take a number. What did the active investors make before costs? It has to be the same number. So, before costs, the total market made 12%, the indexers made 12% and the active investors made 12%. After costs is a different story. A well-designed index fund should have a very low cost of management. It should also have very low turnover, very low transactions costs. Actively managed funds by their very nature have higher management fees, they employ more skilled people. They also have transaction costs because they're active. So, after costs, the average passive investor must outperform the average active investor. That's just arithmetic.

以美股作分散投資,夏普的簡單數學邏輯就是買美股指數基金。

香港亞太研究所經濟研究中心成員

美國克林信大學經濟系副教授及資訊經濟計劃附屬學者

http://www.facebook.com/economics3.0

 

(編者按:徐家健教授最新著作《經濟學說藝術投資》現已發售)

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