Monday, November 19, 2007

小心睇完會改投資觀

孫柏文呢排反覆諗「Black Swan黑天鵝」概念。相信大家都知,話一件事係黑天鵝,等於呢件事有三大特點。博客Moneycafe解得最好:

1.事出突然,發生前完全預計唔到。
2.影響深遠。
3.不過發生之後,就好多人提供好多合情合理嘅解釋方法,話:「一早應該預計到啦!」

好多人鍾意用911做「負面黑天鵝」嘅例子。將黑天鵝概念發揚光大嘅Nassim Taleb,就鍾意用互聯網、雷射、電腦嘅興起做「正面黑天鵝」嘅例子。呢幾日,博客Moneycafe就諗:「今天金融市場複雜得令人害怕……到底次按危機係咪黑天鵝?」我亦應承今日答佢。孫柏文可以斬釘截鐵咁話:「Depends!」

大家睇到呢度,相信又想「網絡欺凌」我。應該已經破口大罵:「Depends?咁係咪黑天鵝先?」其實一件事係咪黑天鵝,取決於觀點與角度。

「慘過八萬五」

Taleb 喺佢本書裏面講過兩個人。第一個就係投資銀行裏面嘅典型統計學博士。第二個就係投資銀行裏面,由「派信仔」做起嘅高級炒家。

Taleb話如果你問佢哋兩個:「有隻銀仔擲毫連續開咗99次「公」,咁第100鋪開「公」嘅機會率又有幾高?」統計學博士就會話:「擲毫,下次開「公」或「字」嘅機會率都係 50%。」相信你呢個懶醒fan屎都係咁諗。

不過高級炒家就會話:「連續99次「公」?個銀仔肯定有問題啦!第100鋪肯定都係「公」!」

將佢哋嘅分析伸延,如果第101至200鋪都係「公」,對於統計學博士嚟講係一次黑天鵝,因為佢用嘅計算程式model話每鋪「公」得50%機會。

不過對於個高級炒家就唔係,佢未必知個銀仔嘅問題喺邊,但係因體現咗《信報》曹sir嘅「有智慧、不如趁勢」,所以贏大錢。

今時今日,喺各大投資銀行裏面嘅統計學博士,可能覺得每張次按債券爆煲機會得50%。因為呢個係用佢哋嘅model計算出嚟。問題就係100張裏面,已經有99張爆煲,不過如果問第100張會點。佢哋一定話50%冇事。

所以對嗰啲信投資銀行「專家」嘅人,次按危機係黑天鵝。不過,對《金手指》fan屎就肯定唔係。舊年已經話過「花旗國樓市將慘過八萬五」!

13 comments:

  1. 孫公:

    請諒小弟聽到呢個Black Swan Theory 聽到...唉。

    就咁講,以你轉述Moneycafe第二個解釋:影響深遠。

    既然影響深遠,就即係代表“以後,甚至一段時間以後先會發現到有影響。”黑天鵝的出現就一定係後之後覺(仲要好後好後),而唔係一見到黑天鵝就知道有黑色既天鵝。

    係呢個情況,小弟覺得黑天鵝概念,只不過係Paradigm Shift 概念既孖生仔(根據正面黑天鵝說法)而負面黑天鵝,只不過就等於“Surprises”。

    不過點都好,今次伊隻黑天鵝,恭喜你,或者比你捉倒囉!

    ReplyDelete
  2. 點講呢?

    正如九一一前有FBI話收到風,知道有情報話有恐怖襲擊。當然,結果係無人理佢。

    因此當孫柏文提出「花旗仲大鑊過八萬五」時,信者當然得救,但信者又有幾個?

    BLACK SWAN強調,能預測黑天鵝出現的機會微之又微,因此與其花時間作預測,不如更好好分析處理黑天鵝的後果。

    ReplyDelete
  3. Hi Pakman,

    Re: 「自瀆」文章 周年紀念http://phatdat.blogspot.com/2007/07/blog-post_7062.html

    The characters in this paper cut http://2.bp.blogspot.com/_AlX-SMM9wjg/RqdAG8QFsYI/AAAAAAAAAn8/dH2zFl2dB9c/s1600-h/20070725a.jpg was too small to read, do you mind to post it out again? Thanks

    Cheers,
    Bravo

    ReplyDelete
  4. http://2.bp.blogspot.com/
    _AlX-SMM9wjg/RqdAG8QFsYI/
    AAAAAAAAAn8/dH2zFl2dB9c/
    s1600-h/20070725a.jpg

    ReplyDelete
  5. 覆moneycafe:

    一如日軍空襲珍珠港,果陣中國國軍軍統一早譯破日本電碼,日軍飛機飛到夏威夷雷達反應範圍,但美國都唔信日本真係咁賭一鋪,結果咪炸到Pearl Harbour阿媽都唔認得。

    但珍珠港美國善後得好,下定決心全力同日本砌一鋪,正面定負面查實睇你點處理。

    ReplyDelete
  6. 唔好怪我多嘴了。

    你一個星期出5篇文,一年出二百幾篇。現在次按出現問題影響樓市,和你二百幾篇其中一篇有相同預測,你便認叻地標榜自己。

    試想想,放二百幾個地雷,我都信實有幾個中的。

    依排我成日得罪人,但又忍唔住口。睇完我留言不悅請見諒。

    ReplyDelete
  7. 我以為冇邊個會太認真對待柏文之意見。

    因為只要你之前相信他任何一次“一注獨贏”或“一注獨沽”,早已輸到內褲都要檔埋,仲邊會有機會再聽他第N個意見。

    Pak Man的文章獨到之處,就是經常刺激大家逆向思維,反思考其論據之不足,對讀者有很大裨益,所以其讀者有增無減,再加上“camera face”,又有Money Cafe,Apple Daily又開 live broadcast 俾佢。

    真係發到豬頭咁,
    Congratulation, Pak Man

    ReplyDelete
  8. 孫公:

    查實我呢度要多謝Bravo,因為我琴日搵左你篇文好耐都唔知係邊(我仲搵2006年添)。不過坦白講,d字真係好細。

    唔好介意,小弟想你幫幫手:

    1. 將你右邊個Blog Archive 個sorting變做by month or by week。(By day 好難搵)

    2. 小弟一直通過RSS FEED睇閣下大文,如果可以,set 番可以閲讀全文,咁小弟就唔洗睇到到喉唔到肺。

    (查實應該係班統計博士set錯model,應該由佢地善後就啱)

    ReplyDelete
  9. Hi Pakman,

    I think it is about the right time post out all those 2006 missing passages, I think there should be quite a number of useful black swans inside. Each piece was a serious product that worth archiving. Whether those black swans will survive depends on many factors, no need to take it too serious, isn't it?

    Hi CM,
    Thanks :) as I too wish to read the 1st black swan identified. But it was too small to read...I guess the grown up black swan now looks quite different from its baby look.

    Cheers,
    Bravo

    ReplyDelete
  10. So you kids want to read that piece that appeared July 21 2006?

    Let me try to dig it out...

    ReplyDelete
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