講了兩日經濟,今天來個娛樂性較高的題目—無線劇集的影響。

講到無線,大家可能會馬上切齒力數其劇集如何的不爭氣,質素江河日下,但有沒有想過背後其實可能有著精密的盈利計算?中大經濟系的陳卓賢、陳顗光和李俊傑同學就此分析了無線過去十年的財務報告。也許是一台獨大的關係,無線的節目製作成本和收視率的關係不大,但和盈利的關係卻十分顯著:製作成本每上升一元,無線的香港業務盈利就平均下降一元二角(左上方表格)。在這情況下,若你是無線的管理層,就算你心裡明白一分錢一分貨,你又如何向股東解釋提高製作水平的必要?

說到不思進取,網上廣傳無線將重播經典金融劇集「大時代」。一提起這套劇,一眾股民想必都在心裡高呼「小心『丁蟹』!」。所謂「丁蟹效應」,是指每逢有鄭少秋參演的電視劇播映,股市都會應聲下跌。說到這裡,不得不提中大經濟系的一名傳奇舊生。他幾年前還在學的時候就已經在網上聲名鵲起;筆下的金融言情文章可謂風靡一時。不說大家不知,這位舊生畢業前特地花了一個學期鑽研「丁蟹效應」。

那「丁蟹效應」到底是真是假?左下方表格是秋官劇集上映對恆指的平均影響,很多個零的那個就是了。這說明「丁蟹效應」基本上並不存在。當然有人會說,效果要長期才浮現,所以右下方的表格就估算了恆指在秋官劇集上映後的反彈幅度。反彈雖看似存在,但在統計學上並不能從市場的噪音中分辨出來。

其實從經濟學的角度看,「丁蟹效應」不明顯很合理。因為若效應真的存在,以買賣為生的一眾投資者定必會在上映前蜂擁沽空恆指,以期高賣低買圖利。但這一來股市遠在上映前就已經下跌,「丁蟹效應」也就不會出現。大家若明白這點,也就掌握了「有效市場假說」(Efficient Market Hypothesis)的中心思想。

專題展覽之二:最低工資

昨天談了「下下幾十萬上落」的股市,今次輪到一個和低下階層息息相關的經濟政策—最低工資。

最低工資的基本理論分析,所有讀過經濟學入門的人都一定知道—強制最低價錢會減少買家的需求量,交易量亦隨之而減少。也就是說,最低工資應增加失業率。

理論是這樣,實際上又如何呢?中大經濟系的張梓錕、黎帝輝和吳沛恩同學參考了統計署的《收入及工時按年統計調查報告》,發現領取最低工資的僱員人數自法例實施以來有下跌趨勢(見左上表格)。不過下跌是否因為僱員被解僱?那又不一定 。更有可能是因為市場工資續漸高過最低工資,以至最低工資失去作用(右上表格)。

潘德軒、詹詠森和姚蔚真同學的專題就保安員這一行業作了較深入的研究。從左下角第一幅圖表可以看出,在最低工資有所調整的2011及2013年,保安員的工資的確有顯著升幅。不過第二幅圖表的數據就顯示保安員的就業率非但沒有下跌,甚至還有上升的趨勢。大家可能以為這是新樓宇落成量造成的影響,但從第三幅圖表來看,這顯然並非主因。

最低工資不減就業,經濟學界亦曾就此有過一番爭論。雖然如此,經濟學家一般都同意現行的最低工資對失業率影響細小。事實上自從最低工資實施以來,已經有多位中大經濟系的同學以各種方式估算過香港最低工資的影響—比較實施前和後、比較各行各業、比較香港和外國等等—得出的結論基本上都是最低工資無甚影響。

專題展覽之一:中港股市

今日先談談大家最關心的中港股市。近日港股升幅凌厲,不少分析都認為是由內地公募基金經滬港通入市帶動。那港股到底有何吸引?其實過去大半年來上海股市已翻了一倍,港股市值相對起來自然偏低。

中文大學經濟系張凌俊、何定謙及李俊軒同學的專題探討了國內股市近年的起伏和各經濟指標的關係。由圖表可見,上海股市近期的升幅和內地的國民生產總值及貨幣供應量無甚關係,甚至連名聞遐邇,由貸款量、貨運量及用電量組成的「李克強指數」都解釋不了這升幅。

在這背景下,滬港兩地都有掛牌的股票有沒有在兩地同時上升呢?由封璟、呂珮婷、郭璇及裵智仙同學所作的專題估算了滬港通實施前後兩地股價的關係。在滬港通實施前,當一隻兩地都有掛牌的股票在上海升1%,在摒除兩地大市的整體走勢後香港相應的股票平均上升0.3%。在滬港通實施後這關係雖變得更強,但直至二月亦只增加了不到0.02%。這當然是因為在三月之前,滬港通南下流量甚低。

時至四月,滬港通終於起上作用,港股今後會否會隨內地股市變得更波動?那就有待下年的同學去研究了。

中文大學經濟系本科專題展覽

由香港中文大學經濟系主辦的第一屆《經濟系本科專題展覽》將於2015年4月15 – 21日假利黃瑤璧樓地下大堂舉行。展覽將展出近六十組探討不同經濟議題的專題習作,而在15號和16號早上更會有近百名本科同學親身講解。活動亦邀請到本系兩名傑出青年學者—信報《經濟3.0》作者梁天卓教授及2013年度中大模範教學獎得主莫啟聰教授—分別在4月15日及16日主持開幕講座。

是次展覽的其中一個目的是為了讓大家認識經濟學研究其實是非常多樣化。在接著下來的數天,我會在這裡和大家介紹數個將會展出的習作作為例子。

Small facts about MS Office

– Docx equation editor does not automatically italize characters you if are entering with a non-Romanized input method, even if the characters you enter are alphabets.

– Excel .MMULT function requires the two inputs to have the same dimension. You can use it to multiply two 1-dimensional arrays or two 2-dimensional ones, but multiplying a 1D array with a 2D one will fail with an “unable to get the MMult property of the worksheet function class” error. The practical meaning of this is that if one of your input is just a vector, you still need to declare it as a 2D array.

穿了數年的褐色皮鞋快要斷開成兩截,竟然給我在先施清貨中找到同一款式。嘿,這樣就為我省下了不少時間,就當從沒換過好了。
(貓咪:那舊鞋是給我當玩具吧?我最喜歡抓鞋帶的了!)
With my brown leather shoes in need of replacement after years of service, I was pleasantly surprised to find the exact same pair of shoes on clearance in a department store. Now I can just pretend I am still wearing the old ones.
(Cat: “So I get to keep the old shoes? I just *love* pulling shoelaces!”)

本土經濟學研究

由樓市辣招到汽車登記稅,政府的很多政策都明顯違反了基本的經濟邏輯,原因何在?官員不濟、政客左右也許是主因,但本地經濟學者也有相當責任—相對其他地方,香港的經濟學者的確甚少研究本土議題。在歐美以至中日,幾乎每一項和錢有關的大型政策都有經濟學家研究。紐約時報不久之前就有一系列報導,探討經濟學在近年如何壓倒其他社會科學,主導了美國的政策討論。*

誠然,由本地經濟學者撰寫的評論並不罕見。早年有張五常,後有雷鼎嗚、莊太量等,近年則有經濟3.0的三位同行。這些本地經濟學者多年筆耕,為經濟學開拓本地市場功不可抹,但評論終歸是評論,和嚴謹的學術研究不可同日而言。

後者的缺乏,歸根究底其實也是政策問題。多得港大陳文敏教授被打壓的新聞,公眾對教資會如何向各大學分配經費有了多一點了解。在現行機制下,一個學系所得的經費有一大部份是和「研究成果」掛鈎,而像經濟學這種沒有直接商業價值的研究,「成果」是看有多少篇論文發表在國際頂級學術期刊。因為這些期刊多是在歐美審編,有關香港本土的研究獲青睞的機會微乎其微,老師們為保生計,自然不會花時間做本土研究。當政策只求數字上「超英趕美」,社會政策研究就被犧牲掉了。

*http://www.nytimes.com/2015/01/24/upshot/how-economists-came-to-dominate-the-conversation.html

Windows 10

Windows 10終於有內建多重桌面,感覺亦較一致。Start menu其實係縮小版嘅start screen。Cortana暫時無料到。

It has always bewilders me that Windows do not have built-in multi-desktop functionality. Now Windows 10 is finally going to have one.

Overall Windows 10 feel a lot more consistent throughout then Windows 8, which feels like a forced blend between a screen-friendly interface and traditional mouse-based Windows. For example, A lot more settings are now available in the Win8-styled “PC settings”, though the good-old Control Panel is still here. My guess is the latter will be gone in the release version.

Start menu is back…sort of. Microsoft essentially scaled-down the Windows 8 start screen to get a hybrid between the old and the new.

Cortana is pretty much just a shortcut to Bing at the moment, not much to see.

經濟夫婦過情人節

我和內子都是教經濟,情人節是怎過的呢?

其實,經濟學家最在行是套利(arbitrage)。情人節當天預先紮好的花束是非常的貴,但散買的價錢是和平日一樣的。同樣,當日外出享用西式晚膳很貴,但酒樓茶記價錢不變, 在家下廚就更是加分殺著。

以今天情人節正日為例,花墟十支玫瑰連襯花,紮好要六百元,不連襯花也要三百元。散買呢?九十元—二十支。一束花三分之二的價錢去了包裝,是否值得見人見智,但若你一年只會紮一次花,那就應該在差價最大的今天紮。同樣,若你一年只會下一次廚,今天絕對錯不了。

那DIY到底有多便宜?以下為我倆今天的支出:
花盒:黃紅色馬蹄蘭$95 、紅色小玫瑰$90、沙巴葉$20,共$205。
芝士火鍋:芝士$20 、麵包$10、有機沙律菜$20等等,約共$100。

 

Powerline Network Adapters Hands-On

Most people have probably faced the problem of not being able to provide good Wi-Fi coverage for every room at home, and this problem is particularly severe in Hong Kong due to the use of concrete walls. In the past one would consider wiring the rooms with Ethernet cables or installing Wi-Fi extenders.  Today I am going to review a third option: powerline network adapters. They work by sending signal through electricity wirings, and units plugged into sockets under the same meter and will automatically form a network. To get internet access, simply connect one of the adapters to your broadband router with an Ethernet cable. Furthermore, there are Wi-Fi-broadcasting models that allow you to extend Wi-Fi coverage.

This hands-on features kits from two Chinese brands: a budget model from Tenda and a mid-range model from TP-Link. Budget models differ from higher-end ones in two major ways: First, budget models usually have maximum theoretically speed of 200Mbps, whereas higher-end ones have speeds up to 600Mbps. Since these numbers are theoretically limits, practical speed will only be a fraction of that, as my test results will show below. Second, high-end models sometimes have a pass-through socket that could be a life-saver if your room is in short of wall sockets.

Test models: Tenda P200/P201 kit (~HK$460) and TP-Link TL-WPA4230P Kit (~HK$650). Each kit comes with one cable-only unit and one Wi-Fi-broadcasting unit.

Test environment: Hong Kong Broadband 100M connection. Test conducted with speedtest.net with a Fujitsu Q584 tablet.

Basic installation: Easy. Both kits work immediately once I plug the included units into wall sockets.

Advanced Installation: you can build a network where devices roam between different Wi-Fi sources depending on their strength by setting the same SSID, encryption mode and password for all Wi-Fi access points on the network. The TP-Link unit has a button for automatically cloning my original Wi-Fi router’s settings via WPS, whereas for the Tenda unit I need to manually change settings via a browser. In practice I have never found WPS particularly easy to use, and it took several tries before the TP-Link unit was able to clone settings successfully. Furthermore, for unknown reasons I could not access the TP-Link’s settings panel the way the manual describe.

Speed: My HKBN connection has an average speed of around 60Mbps. Plugging the powerline units directly into wall sockets, I got the same speed with the TP-Link unit, whereas for the Tenda unit I only got 30Mbps at best. The results were the same regardless of whether I use an Ethernet cable or Wi-Fi, so the bottleneck is the Tenda unit itself. Speed drops dramatically if you plug the units into an extension cord—the average speed was only 3Mbps in my test.

Conclusion: Powerline network adapters present a very convenient way to extend your home network. Base on my test results, I would recommend spending the extra money to get the higher-end models due to the large speed difference.