Tag Archives: social network

to be an eBay seller...and explore the social network effect

It is interesting to work for eBay; however, most of the time I am looking at the massive data without really thinking about how they are generated... for instance, I have no idea how difficult it should be to be a successful seller on eBay. It somehow sounds a little wired that we talk about mechanism design (say, whether eBay's ecological system is better than Taobao's) without personal experience.

To step in, I should try - and there was a precious opportunity for me to do so! After the China-R conference in Beijing, two professors from Australia (Graham Williams and John Maindonald) asked if they could buy additional packs of the playing cards somewhere so they could share with their colleagues and friends. Then why not on eBay?

Then I typed "ebay.com" in my browser... log in...sell...The photos were prepared several months before... upload... done!

However, when I was trying to copy the link...it was so long!


Then I noticed the lovely "share to twitter" button on the left ^O^ Let me just use this one!

A simple click leads to a new tweet... of course I need to at some useR... Yihui should be the best choice 😛

Not sure what has happened during the night... when I wake up next morning, they are almost sold out (I listed 10!). Well... then the painful shipping process comes. Thanks to the fantastic e-packet tool(http://shippingtool.ebay.cn), it was pretty convenient to complete shipping online. OK, the postman will take care of them. Goodbye, my cards...

The special benefit is that now I realize how powerful the social network could be. Without spreading information through twitter, it would be much slower if we manually copy and paste the URL in emails. Social network sites control it just in the right way - "word of month" helps customer selects goods based on their reliable information source. Some comments:

Karthik Ram@_inundata 30 May

Totally bizarre #rstats playing cards for sale on @ebay. http://bit.ly/18BmwTg 

Geoff J@geoffjentry 30 May

@_inundata I once bought a "used wife" on @ebay yet somehow this is odder.

Ok...is it that wired?

BTW, the integration of eBay site and twitter is pretty good. Once the link is attached the listing image also appears. See below.2013-06-04 14_11_43-Karthik Ram (_inundata) on Twitter

Getting Close to China!

I don't know why, but recent days I have seen so many papers on China - both from the historical and modern perspectives. Today I was so lucky to enjoy Noam Yuchtman's presentation on two of his papers:

“Teaching to the Tests: An Economic Analysis of Educational Institutions in Late Imperial and Republican China”

“Intergenerational Mobility and Institutional Change in 20th Century China” (with Yuyu Chen and Suresh Naidu)

Both of them are revelant to education, but from differnet angles. The first one focus on the historical sharp change in the education system (the abolishment of the traditional system, 科举制度), and the establishment of modern studies on polyscience in China. He uses the individual level data of employees from the Tianjin- Pukou railway company and checks the difference in wages and departments among people with different educatoin backgrounds. The second one exams the intergenerational mobility regarding the insituitional change during the 1949 (the establishment of the People's republic of China) to the 1978 (the reform). That is really interesting...

The Jinpu Railway actually passes Jinan, haha! However, it is a shame that the old Jinan railway station was deconstructed in 1992! I have never seen the real building in my life!!! Here is just a photo as a momory.

A few days ago I also read an article related to Chinese people, and it is a doctoral thesis of Xiaohuan Lan:

Permanent Visas and Temporary Jobs: Evidence from Postdoctoral Participation of Foreign PhDs in the U.S. (2009)

The Prevalence of Low-Paid Postdoctoral Positions: The Impact of Foreign PhDs on the Wage of Natives. (2010)

Visa Policies and Research Productivity of Postdocs in the U.S. (2011)

The brief introduction from the  author is available in Chinese on his blog. As you can read from the title, it is about the Green Card and the post-doc market. In the labor market it is always interesting to see the impact of policy changes.

OK.... Overall, it is always nice to enjoy great papers answering interesting questions. Acutally I'm also writing a paper on China now. It is about an innovatoin in the financial system in the ancient China. Hopefully I can get some intersting results! Although most time I care about social network, or theories, it is also great to have the chance to do a research on CHINA! With so many great historical records, I don't really understand why there are comparably only a few papers...hence, no matter how little my contribution is, I would like a try!

Expectation, epidemics and the social network

As the final master project, I set "social network" as one key word, not surprisingly. Then I need a context to apply to.

Actually I began to think about the topic from last Christmas. However, things were not going as well as I expected. A few months later I posted a notice on my chinese blog and was looking for someone to collaborate on this. Unfortunately, not that ideal either.

Now there is only one month left for me to work on it. Moreover, I also noticed that the 4th Chinese R conference is going to take place on the 28th of May. Well, since social network is one topic on the list, I really want to go back and see what's going on. Ideally, if I can finish the paper by 21th of May, and I can also find a funding for this trip, I would like to go back to China for a few days and give a speech... Well, then time is pretty tight, and I don't know even where I can ask for money. Does UPF or BGSE have a flyout funding? Any helpful informaion?

Well... a little off topic. This time, we found several great papers to follow. Before, I was only reading Jackson's book on social and economics networks, so I knew nothing about health. Interestingly, there are more people from sociology who are working on social network. Checked out some demographic journals,  tons of relevant papers appear.

However, although we have got enough idea now and it seems to have a possible way, still there are a lot of questions remained. As I wrote down a year before, my idea is concentrated around "information". In particular, here I want to try to stress the importance of information on expectation. From the context's view, when it comes to health, people tend to be either over optimistic or passive,  and as a result, the risk is either overestimated or underestimated. From the common sense, if people do not hold a nearly correct expectation, then for sure, their behaviors  will diverge from the optimal path. This time, I want to find out the way to model this process, and further, check the validity of the model by some empirical methods.

Maybe now, most challenges lie in the concern of time. Somehow luckily, I only have two courses to take this semester, which ensures more free time for me to work on a project. But still, I don't know how much I can finish. Things are going more and more stressful.

Among all issues related to (public) health, this time we may pick some epidemics, and a good choice should be HIV/AIDS. HIV has become such a hot topic in recent years, and as a sexual disease, it does have a lose link to social network, or specifically, sexual network, including the homosexual and heterosexual ones. Moreover, the risk perceptions of HIV/AIDS will also influence or even determine corresponding sexual behaviors - that's may be a reason why there are so many public targeted education in countries all around the world.

Hopefully I was not too optimistic this time (otherwise for me, I cannot follow the optimal path as well ^_^), and also, not too ambitious. Learning by doing, that's how we will benefit from this project.

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.