Quantile Regression

Caution: If you are not an economist (or a social scientist of quantitative type), please skip this post.

Read Deaton (1997) (pages 80-83) to review the merit of running quantile regression.

1. Uncover the heteroskedasticity in the error term.

2. Figure out the shape of the conditional distribution (such as income conditional on age).

3. Obtain a more efficient estimator than OLS when the error term does not follow the normal distribution.

There is a concise survey of quantile regression in economics: Roger Koenker and Kevin F. Hallock (2001).

For an instrumental variables estimation of quantile regression, see Chernozhukov and Hansen (2005). For a method to estimate the the impact of a regressor on the unconditional distribution of the dependent variable, see Firpo, Fortin, and Lemieux (2007).

Week of an assistant professor

Push a little bit forward the autocracy network project, joint with a PhD student of my Institute, by reading some published papers on social networks (hence this post) and by listing up the members of the Presidium of the Romanian Communist Party since 1965 until 1974 from Keesing's.

Spring has finally come

Spring finally came to Stockholm today, because the wind is not freezing anymore and the night temperature does not go below 5 degrees. A coat is no longer necessary even at night. And we have 15 hours of daytime right now.

Tabbouli

For dinner with today's seminar speaker, we went to Tabbouli, a great Lebanese restaurant in Stockholm. This is my fourth visit to the restaurant, and the food is always good.

They serve Lebanese wine only (with exception of a couple of South African for some reason). We tried Château Ksara's red wine, and I liked this wine a lot. As I don't have good vocabulary for describing the taste of wine, I just let you read the description of the wine by Ksara itself (a pdf file). I also tried a cup of Lebanese coffee after dinner, which was brilliant with cardamon flavor. (Here's how to brew Lebanese coffee.)

If you don't know what to order because you're not familiar with Lebanese cuisine, just order the set menu at the back of the front page of the menu. That fills your stomach completely.

Bloch, Genicot, and Ray (2008, JET)

The paper's abstract is available at http://dx.doi.org/10.1016/j.jet.2008.01.008.

Consider a village in a developing country where households engage in bilateral insurance schemes with directly connected households (relatives or friends, for example). If a household deviates from the insurance scheme (ie. fails to transfer money to directly connected households that have negative income shocks), the victim household will tell such behavior to connected households who in turn terminate the insurance scheme with the deviating household as a punishment.

The question is what aspects of the household network characterizes a stable household network, that is, a network in which no household has incentive to deviate from the bilateral insurance schemes.

Denote by q the number of links that the victim's information is passed through. For example, q equals two if the victim tells its directly connected households which in turn tell their own directly connected households, but the information does not spread beyond that.

Then the stable network is characterized by the maximum length of the smallest cycle connecting any three households in the network being q+2.

Why? Suppose household i fails to transfer money to household j. Household j tells its suffering to its connected households with the path length of less than or equal to q. These informed households cut the link to household i. Since the length of the smallest cycle of any three households in the network is at most q+2, the information from household j reaches all the households with (direct or indirect) links both to i and j. As a result, household j will be cut off from the network that includes household i, by deviating from the insurance scheme. A smaller network yields a lower payoff (intuitively, pooling income risk among more households provides better insurance against negative income shocks). Therefore, household i has no incentive to deviate, which means that the household network is stable.

Day of an Assistant Professor (79)

Finish revising the African democracy paper and submit it to a journal. It took more than 6 months after the first rejection.

Day of an Assistant Professor (78)

Revise the African democracy paper.

Join a birthday party held by a PhD student of my Institute at his apartment in the evening.

Day of an Assistant Professor (77)

Revise the African democracy paper.

Attend a seminar.

Book flight tickets for the business trip to UK next month.

Day of an Assistant Professor (76)

Meet a PhD student to talk about his research ideas.

Resume the long overdue revision of the Africa-democracy paper.

Day of an Assistant Professor (75)

Prepare the presentation later today.

Give a talk on the climate project at my own department's seminar series with my colleague. After that, discuss with my colleagues the comments we received during the talk.

Day of an Assistant Professor (74)

Prepare for tomorrow's presentation on the climate project.

It's Easter Monday, but this kind of thing does not matter to researchers, especially those without a family and/or coming from Asia like myself.

Hotel Review: Bristol Hotel

I stayed in room 504 of the Bristol Hotel in Frankfurt from 10 to 12 April, 2009. It was one of the most pleasant hotels I've ever stayed at.

The hotel is the least expensive one of those listed in Wallpaper* City Guide for Frankfurt (70 euro per night for a small single room, including breakfast). Online booking on its website is very easy and smooth. The email confirmation message says, "A cancellation free of charge is possible until day of arrival, 4 pm."

I arrived in the late morning, but it was no problem for me to check in (I thought I should wait until around 2 pm for check-in). My room was even upgraded to a larger single room.

The bedroom is furnished pleasantly with minimalist design, featuring raindrop-shaped door knobs and hooks for hanging clothes on the wall. The bathroom has a removable shower head and a designer wash basin, with a pitch-white bin by Koziol (there is no shower curtain or bath tub, though). It would be perfect if the bedroom has a kettle for brewing tea. But with good design, such tiny details of convenience do not matter much.

The entrance hall is also well-designed, complete with cow-skin couches and electro music of good quality in the background. The hotel bar serves good food.

The breakfast room, open after 6:30 am, faces the hotel's courtyard garden with lush green tree leaves through large windows, serving not only continental but also English/American breakfast, which is important for someone like me who needs to eat plenty of food in the morning. Food is decent, so are tea bags (Tchibo Coffee Service's Pure Tea Selection).

Wireless broadband connection is for free. Even if you don't have your own laptop, there are two computer terminals in the lobby, available for free. The front desk also lends you a mini laptop by Acer to be used in your bedroom if you deposit your credit card (but again for free of charge). I don't have a laptop and don't intend to email during my stay. But after the amazing experience at Cocoon, I feel like emailing a friend of mine to tell my excitement. The Bristol Hotel just makes my desire feasible for free of charge.

The location is excellent, too. Just a five minute walk away from an U-Bahn station (if you walk via platform 24 of Frankfurt Hbf station). Five minutes of a further walk takes you to airport coach stops on Mannheimer Strasse.

Finally, the hotel staff is all friendly. When I check out, it takes a bit of time for my credit card to be recognized. The receptionist apologizes, a rarity outside Japan.

I'll definitely stay at this hotel if I visit Frankfurt again.

Portikus

A mill house on a sandbank of the Main, which is actually a gallery space for contemporary art called Portikus.

This is a brilliant location for contemporary art exhibition. It doesn't belong to anything else in Frankfurt due to its position on the River Main. People driving or walking on the Alte Brucke bridge (including my friend) won't notice this is a gallery, rather than an abandoned mill house, unless they are curious. I love its solitude in this busy city.

Grosse Rittergasse

A street in Frankfurt

A view from the south bank of the Main

Euro!

What an ugly symbol of euro, standing in front of the Eurotower in which the European Central Bank has offices.

Willy-Brandt-Platz U-bahn station

Saint Bartholomeus's Cathedral

Frankfurt's main cathedral with a planetree, ubiquitous in Frankfurt (especially along the Main).

Saalgasse houses

Lined up on the north side of Saalgasse street are these highly decorative houses.

Skyscrapers in Frankfurt

These are not the most famous ones in Frankfurt, but I didn't have time to visit every skyscraper.
01
02
03
04
05

01 Westhafen Tower, viewed from outside the Bristol Hotel
02 A view on Mainzer Landstrasse
03 Eurotower, viewed from an exit of Willy-Brandt-Platz U-Bahn station
04 Frankfurt's skyscrapers viewed from Untermainbrucke bridge
05 Lindner Hotel & Residence Main Plaza

Born and bred in Tokyo, the view of skyscrapers makes me somehow feel calm. Another reason why I kind of feel uneasy in Stockholm, a city without skyscrapers of any significance.

Cocoon

Everybody tells you Frankfurt is a boring city. That is not true if you are into club music.

Located about 10 minutes away by taxi to the east of the city center, the Cocoon nightclub is said to be one of the best nightclubs in the world (UK's club music magazine DJmag ranks it at the 11th in the 2009 edition of its worldwide nightclub ranking). On the date of my arrival to Frankfurt to visit friends of mine, Monika Kruse, a German minimal techno DJ whose play I've long wanted to experience live, happens to be scheduled to play at Cocoon. There is no reason why I should not go to this club.

And it turns out to be one of the best night clubbing experiences ever. First, the interior of the club. Usually, a night club is rather scruffy. At best, the dance floor room is just a big box. Cocoon's decor is really elaborate. Cocoon-shaped holes in the wall act as a sofa space for chilling out. A balcony in the dance floor room, also shaped like a cocoon, plays a role of the DJ booth, allowing every dancing head to see DJs on the deck. The dance floor has several layers of round-shaped platforms, allowing those seriously dancing to be not interrupted by those just walking from one end of the room to the other. Outside the dance floor is a chill-out space looking like a stylish, trendy bar, a rarity for a truly musically-oriented nightclub.

The bar seems to serve alcohol of good quality, as my shot of tequila is flawless. Around half past midnight, Monika Kruse appears on the white cocoon DJ booth which reflects the projected computer graphic movies along with the surrounding walls of the dance floor. And, most importantly, the club has an impeccable sound system with excellent acoustic, especially for high-pitched sound. Most nightclubs, even those boasting the good sound system like Fabric in London, have the acoustic ill-suited for high-pitched sound. Here in Cocoon, every bit of high-pitched rhythms can be felt clearly. With Monika Kruse's superb mix of minimal techno music, I cannot help but feel euphoric.

Sorry for no photo. I don't bring a camera to a night club because the camera in a pocket is annoying while I'm dancing.

How to buy tickets for U-bahn

Buying tickets for U-bahn, Frankfurt's metro, is horribly tricky for first-timers. Here's what I learned from my friends living there.

For a single ticket within the city center, enter 97 by using number keys. Then press the green button with letters "97 Kurzstrechke". Then pay 1.50 euro.

For a one-day travel card, enter 5000 by using number keys. Then press the yellow, second-to-top button with letters "Tageskarte". Then pay 5.80 euro.

Here's a booklet in English, which says you don't need to enter 97 for a single ticket within the city. I don't know which is correct.

If this is too complicated, forget buying a ticket and you'll run a (rather small) risk of paying the penalty 40 euro if you encounter a ticket inspector. (There's no ticket barrier.)

Frankfurt (Main) Hauptbahnhof

Frankfurt's main railway station. Platform 24 can be used as a footpath between its U-bahn (metro) station and the Bristol Hotel or any other hotels in the area on the north-west of the station, because there is an ungated exit to Poststrasse street on the platform.

Day of an Assistant Professor (73)

Have a discussion with my colleagues on the presentation of our climate project next Tuesday.

Plan a business trip to UK (Edinburgh, Nottingham, and London) next month.

Day of an Assistant Professor (72)

Learn from the RA that there are some problems regarding the data entry work. Figure out how to solve them and give her new instructions.

Have a chat with a PhD student who took my course last year about his research.

Have a chat with another PhD student about our possible joint research. And read papers relevant for this.

Day of an Assistant Professor (71)

Have a chat with my colleague on our climate project, run some regressions to test some ideas we discuss.

Brush up on my math skills.

Day of an Assistant Professor (70)

Submit the referee report.

Have lunch with my colleagues to talk about our climate project.

Work on the climate project.

A brief chat with a PhD student about our possible joint research.

Ask an RA for data entry, which is necessary for the climate project.

Cassina Ventaglio

(Photo source: Cassina's official Japanese website)

A desk designed by Charlotte Perriand in 1972.

Day of an Assistant Professor (69)

Write a referee report.

Email replies to several people in connection to my work.

Mrs Monneypenny

Mrs Monneypenny's column in FT today is beautifully written. A favorite columnist of mine, Mrs Monneypenny's got the knack of writing in a rather short column about several seemingly-different things together in a coherent (and funny) way. This week's one is a good example of this.

Day of an Assistant Professor (68)

Go to Norköpping (pronounced like nor-shopping) by a 1.5-hour train ride for a seminar of the interdisciplinary climate change research project where Japanese urban hydrologists happen to give a talk.

Over lunch after the seminar, talk to a meteorologist on the weather data and to a biologist on the crop yield predication model.

Go back to Stockholm by X2000, Sweden's high-speed train. With my Macbook Air, I try to write a referee report on board. But I have to stop doing it because the X2000 train shakes a lot, making me almost puke.

Day of an Assistant Professor (67)

Work on the climate project.

Receive a request for refereeing. The current backlog: 3 reports.

Spring appears to have arrived in Stockholm today, with temperature rising above 10 degrees celcius for the first time since early November of the last year.

Day of an Assistant Professor (66)

Work on the climate project. What I essentially does this week is to learn biology on how one can predict crop yields based on weather.

Continue the discussion with the PhD student on our possible joint research over lunch.

Attend a seminar.