金融雲端：超支定律 丘亦生
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GS(14)@2013-08-05 23:16:03http://hk.apple.nextmedia.com/financeestate/art/20130805/18364450
西九文化區超支、港珠澳大橋超支、沙中線又超支，無論是基於甚麼理由，大型基建總難逃超支的宿命，這不是例外，是常態，還要是全球現象。
我最近讀到一個學者的研究，結論相當有趣。他認為，基建超支的理由很簡單，主要是有人存心策略性錯誤表述（strategic misrepresentation），用一般人明白的語言講，即是講大話。
歷史上基建超支的例子多不勝數，經典便有超支14倍及延期10年落成的悉尼歌劇院，當然不可漏掉英法隧道，早幾年有人重新估算，得出該隧道對英國經濟的貢獻淨現值（net present value）為負178億美元，內部回報率為負14.45%，結論是唔起好過起。
為何劣績斑斑，主事的官員、一眾顧問還未能從前人的錯誤中學習？反而一錯再錯？
投資銀碼 有人存心誤導
雜誌《大西洋城市（The Atlantic Cities）》最近一篇文章，引述牛津大學一名學者Bent Flyvbjerg的研究，他曾調查全球20個國家共258個大型運輸基建項目，發現十個有九個都超支，鐵路項目的情況尤為嚴重，平均超支45%，最「有譜」的公路項目，亦要超支兩成。整體而言，平均超支28%。
這不能純粹歸咎於預測能力低，如果單單是估錯，照計應會有些高估成本的例子，日後才發現「賺咗」，實際成本比原先預算為低，但實際上這種情況，如鳳毛麟角。
再者，累積經驗多了，超支的情況理應會有改善，但實情是調查的個案橫跨70年，未發現超支情況有任何改善。他的結論是，這些基建項目的投資銀碼根本不可信，有人存心誤導，認真便輸了。
發現超支問題的不獨是Flyvbjerg，連世界銀行多年前也留意到這一現象，甚至把這現象形容為「一切按計劃進行原則」（Everything Goes According to Plan Principle），諷刺官員沒有預設任何可能風險如建造材料漲價等，結果一切總是不按計劃進行。
牽涉利益廣 寧願先上馬
我不完全認同學者的瞞天過海講法，事實上，在估算一個要興建及營運多年的大型基建項目，是有很多假設及空間可供舞弄的。
一個項目上馬，會帶來大量職位及合約機會，可能令人升官發財，所以很多人為着利益，會希望項目獲得綠燈。可是，在議會中，若果報出太高成本，有可能會出師未捷身先死，項目一早被否決，倒不如先報個細數，再把經濟效益描繪得樂觀一點，務求先過議會一關，日後真箇出現超支，即使要申請撥款，項目開了個頭，大家已經騎虎難下，落入沉沒成本的陷阱，難道取消項目回收建築物料？最後還不是附加了一些條件，成立一個甚麼監察委員會，再乖乖的增批撥款，這只是官場潛規則，用不着甚麼工程學或經濟學的解釋。
我很想知，高鐵及西九日後埋單計數，會否又成為另一個經典案例。
丘亦生
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GS(14)@2013-08-05 23:17:15http://www.theatlanticcities.com ... more-expected/6364/
Why Mega-Projects Always End Up Costing More Than Expected
Last week the San Francisco Chronicle reported that the Transbay Transit Center, a massive transportation hub calling itself the "Grand Central Station of the West," will cost at least $300 million more than project officials estimated. One city official characterized the situation as unfortunate but said it wouldn't have a "meaningful impact" on the project. The comment may have been meant as optimism, but it also reflects the fact that enormous cost overruns have become such a normal part of urban mega-projects that they barely even register as a problem.
So how did it get to the point where the only thing we can confidently expect from a big infrastructure project is that it will cost way more than expected?
One thing's for sure: the people who predict the cost of urban mega-projects do a terrible job. Several years ago the University of Oxford scholar Bent Flyvbjerg, who's made a career researching mega-project mismanagement, analyzed 258 transportation infrastructure projects from around the world and found that nine in ten exceeded their cost estimates. The overruns were greater on rail projects than road projects but averaged 28 percent across the board.
What struck Flyvbjerg most about the problem was how very un-random it was. If people were simply very bad at estimating the costs of huge projects, then one might expect some projects to come in under budget and others over. But an under-budget mega-project is about as rare as a dodo riding a unicorn. Instead, wrote Flyvbjerg and some collaborators in 2002, it's more likely that when it comes to mega-projects, public officials engage in "strategic misrepresentation" — aka lying:
The policy implications are clear: legislators, administrators, investors, media representatives, and members of the public who value honest numbers should not trust cost estimates and cost-benefit analyses produced by project promoters and their analysts.
Flyvbjerg's explanation is no doubt true in some cases, but there's also a less sinister reason why people associated with a project might be bad at predicting its costs. From a psychological standpoint, people are saddled with a cognitive bias that causes them to be unjustifiably upbeat (some might say delusional) about the prospects of their own plans. So they do whatever it takes to get them approved — certain that whatever problems have plagued others in the past will be avoided.
Writing in the late 1970s, the psychologists (and would-be Nobel Laureates) Daniel Kahneman and Amos Tversky called this problem the "planning fallacy" . At its root is a tendency for people to see their plans from the inside rather than evaluating them as an external referee might. Whereas an outside observer might consider a project and recognize its "distributional" risks — the combined possibility of a delivery delay or a worker strike or plain bad weather, for instance — the person directly involved might be blind to these possibilities, write Kahneman and Tversky:
The prevalent tendency to underweight, or ignore, distributional information is perhaps the major error of intuitive prediction.
Whatever the underlying causes of cost overruns may be, there seems to be one promising means of addressing them: creating a "reference class" of similar projects to serve as a platform for comparing costs. The idea, as explained by Kahneman in 2003, is that old outcomes can serve as a barometer for recognizing just how unrealistic a biased new prediction might be — and help adjust it accordingly. Such a strategy controls for both political chicanery and cognitive biases alike.
In 2005, Flyvbjerg put this theory into practice at the request of Dutch officials who were considering a massive rail project called the Zuiderzee Line, reported Ryan Blitstein in a great 2008 profile for Miller-McCune. Flyvbjerg predicted that the officials had underestimated construction costs by $2.5 billion and also miscalculated the chance of an additional cost overrun (they put it at 20 percent; Flyvbjerg, at 65 percent). The project was canceled before bids even went out.
Therein may lie the practical flaw with the "reference class" response to the cost overrun problem. More canceled projects means fewer ribbon-cuttings, fewer consulting gigs, fewer construction jobs, and so on. One more thing that's easy to underestimate is the power of the status quo.
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GS(14)@2013-08-05 23:19:32論文