A Piece of Note

Just a quick piece of note before the intensive exam time.

I did not really remember how many seminars I went in the past month... well, anyway. Here is just a note that I have been to Thijs' seminar:

Labour/Public/Development Lunch

Benedikt Herz and Thijs van Rens (UPF)

"Structural Unemployment"

That's really all.... no time to say more, and next week a plenty of interesting seminars are waiting... however, all the exams are waiting there as well... what a painful dilemma~~~

Physics > complex network > link prediction

It is a little funny that while I was trying to build the psychological-economic model in partner matching, two papers appeared in front of me, and they are all about link prediction:

  • Linyuan Lu y Tao Zhou, “Link Prediction in Complex Networks: A Survey,” 1010.0725 (Octubre 4, 2010), http://arxiv.org/abs/1010.0725.
  • D. Liben-Nowell y J. Kleinberg, “The link-prediction problem for social networks,” Journal of the American Society for Information Science and Technology 58, no. 7 (2007): 1019-1031.

Nowadays as an economics student, one important thing you can never overlook is math. That is why sometimes I feel that I am paying more attention to math instead of those economic thoughts. Yes we always stress economic intuitions. However, when it comes to the time problem, apparently math training acquires more time. More important, you may not able to build the entire economic intuition system only through lectures. Outside of the classroom is the place where you can really recognize the sense of how economics is related to people’s everyday life. Newspapers, street talks, and even TV shows may be more helpful.

Well… a little off topic. Today when I was listening to Thijs, suddenly a question not relative to any materials from that course came to my mind. What do we really care? Explanation, or prediction power? Of course they cannot be separated with each other. However, when it comes to prediction, it seems that people care more about the accuracy instead of why this or that method is working well. The best example may be the variety of methods of stock prices predicting. Once when I attended a statistics conference, there was someone who talked about his beautiful “triangle” prediction model of stock prices. For me, it does not make any sense. First, I’m not in the stock market, so I do not care; second, this kind of prediction methods are built above the cloud – there is no foundations which can even partly support the logic beyond the seemly accurate results. It may be unfair to attribute those meaningless methods to physicians – however, more of them studied physics before and they are somehow trying to transplant those solid physical theorems to economics, regardless the fact that economics is a branch of social science, which studies the (economic) functions of the society, the interactions among people and the fundamental reasons behind human behaviors. That is why whenever I see any model directly related to physics, I’m more careful about the economic implications behind the model: at least it should not be contra-intuitive.

Now myself is trying to borrow something from physics…. Obviously the first rule for me it to be as cautious as I can. In particular, I am trying to apply the link prediction idea to economic and social network analysis. Somewhat like the debate about reduced form and structural form in econometrics, I do not want to lose the micro foundations and economic intuitions behind the fancy model itself. It is easier if I just want to predict the result, but with consideration of internal and external validity, the model should be granted with more explanation power, which can conquer the difficulties originated from the complexity of the real society. Actually, I am fond of the name of this branch of science – complex network. How can we abstract simplicity from the complicated world? That may be the common question confronted by every single branch of science, no matter social science or hard/natural science. Without idea experiments in social science, how far can we go? It is really a difficult question to answer….

Anyway, hopefully I can find out a way to introduce link prediction ideas to my naive economic model. It is always interesting to work on the boundary of two different fileds, and you are tasting something new. However, the exams are coming so fast... need to focus on reviewing first.... Will update more later.

Barcelona under the wind

Today it rained a lot. I haven't seen this kind of heavy rain and strong wind here for a long time. Usually, in this kind of bad weather, I would not leave my warm room. However, it is the exam season now so there are a lot of works to do. Among all tasks, I have to go to campus and discuss the research proposal with one classmate. Actually we have found an attractive topic and are trying to combine economics and psychology as close as we can. Then, with the game I designed, no idea how to solve it... That is to say, some assumptions should be simplified in order for us to get a very good intuition about what is going on. It is a pretty interesting process, and we are really enjoying it.

Well... since I had to go to campus, I left my room in the afternoon under the heavy rain as normal. However, when I passed the twin building near Port Olimpia, the cloud above my hear shocked me. The last time that I saw cloud at such a close distance was last summer when I climbed the famous Mount Tai before came here. The difference is that, last time I was out of the city, so I was well prepared for the natural's magic; but this time, I was not expecting anything. Then, I could not stop myself from taking a turn to the opposite direction from school and go to the beach. The wind was really strong at that time, and the sea was not peaceful at all, compared to how it usually performs - actually I don't understand why the sea here is so peaceful. The waves were trying to show its anger, which had been stored for months. Although I had an umbrella in hand, it did not help at all. My shoes got wet, the mercyless rain drops hit me from every possible angle, and the wind blew as a crazy man...

I do not know which side of the sea I should love more. It was too peaceful as nothing would make a difference, so there would be no surprise. However, when it gets mad, I do not know whether I can stand the pressure. At least, I have seen both sides of the sea, and fortunately I did not miss it. That's fine than none.

Intuition vs strictness

Just finished a very interesting class. Thijs was talking about contraction map, which should be the forth time for me to see it in class (-_-!), but there was another "big guy", who was so good at math (perhaps due to the reason that he was from and had been taught in France) that he could not stand the assumption that some economists made for the applications here. Then, I got the honor to listen to their "debate". Haha...

Maybe there are only two kinds of economists in the current academia: those who are extremely good at mathematics, and those who have been granted wonderful intuitions by somebody (maybe the god? but they may refuse to acknowledge the existence of any god). Well, if you would like to count the union and complement of those two sets to be really strict, there must be the third and forth sets - in the forth set, let's simply define it as a collection of outliners who are talent at neither math nor economic intuitions, but succeed anyway from some perspectives…. I’m so sorry but the only people who can be categorized like that I can think of now, are those so-called "media mogul" and live on their speech instead of academic contributions. But let’s ignore them here to make the world simpler 🙂

As I just said, the student in class who asked those technical questions was very good and strict at math – actually that might be the way to define whether you are really good at math: apart from those mathematical intuitions, the level of strictness shown from the way you speak can tell people what kind of formal math trainings you have received. In contrast, I don’t really know how good Thijs is at math, but he usually prefers the way to explain things intuitively – and his intuition is amazing! I don’t think it is common to find a macro guy who has that kind of great sense, or the feeling of “touch”. Then, if you combine both together, you can expect what great talk will emerge!

But to be honest, when I was listening to their opinions, although the natural reaction at that time was to smile and enjoy the debate, after it, especially now, I’m feeling somewhat upset. Which one can be cultured? The ability of math? Sure, but how long will it take if you failed to start from the very beginning? Intuition? I have no idea whether people born with that talent or it depends on the way you learned economics. Sometimes I’m worrying about I’m standing at somewhere in the middle – not really good at math, and haven’t been granted the direct sense of the real economic world. Thus, is there still any possible way left for me to do some decent work in the world of economics? Maybe it was fortunate that my foresight was not too bad: at least, I named this blog as “explore the world of economics”. Whatever I have explored, they will not put any actual constraint on myself.