We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

Random graphs

Trust: The Social Virtues and the Creation of Prosperity

The four Visegrad states — Poland, the Czech Republic, Slovakia (until 1993 Czechoslovakia) and Hungary — form a compact area between Germany and Austria in the west and the states of the former USSR in the east. They are bounded by the Baltic in the north and the Danube river in the south. They are cut by the Sudeten and Carpathian mountain ranges, which divide Poland off from the other states. Poland is an extension of the North European plain and like the latter is drained by rivers that flow from south to north west — the Oder, the Vlatava and the Elbe, the Vistula and the Bug. The Danube is the great exception, flowing from its source eastward, turning through two 90-degree turns to end up in the Black Sea, forming the barrier and often the political frontier between central Europe and the Balkans. Hungary to the east of the Danube is also an open plain. The region is historically and culturally part of western Europe, but its eastern Marches now represents a vital strategic zone between Germany and the core of the European Union to the west and the Russian zone to the east.

Economy and Society

The structure

'Institutionalized Organizations: Formal Structure as Myth and Ceremony', American Journal of Sociology, 83, pp. 340-63.

Data about migration flows are largely inconsistent across countries, typically outdated, and often inexistent. Despite the importance of migration as a driver of demographic change, there is limited availability of migration statistics. Generally, researchers rely on census data to indirectly estimate flows. However, little can be inferred for specific years between censuses and for recent trends. The increasing availability of geolocated data from online sources has opened up new opportunities to track recent trends in migration patterns and to improve our understanding of the relationships between internal and international migration. In this paper, we use geolocated data for about 500,000 users of the social network website "Twitter". The data are for users in OECD countries during the period May 2011- April 2013. We evaluated, for the subsample of users who have posted geolocated tweets regularly, the geographic movements within and between countries for independent periods of four months, respectively. Since Twitter users are not representative of the OECD population, we cannot infer migration rates at a single point in time. However, we proposed a difference-in-differences approach to reduce selection bias when we infer trends in out-migration rates for single countries. Our results indicate that our approach is relevant to address two longstanding questions in the migration literature. First, our methods can be used to predict turning points in migration trends, which are particularly relevant for migration forecasting. Second, geolocated Twitter data can substantially improve our understanding of the relationships between internal and international migration. Our analysis relies uniquely on publicly available data that could be potentially available in real time and that could be used to monitor migration trends. The Web Science community is well-positioned to address, in future work, a number of methodological and substantive questions that we discuss in this article.

http://zagheni.net/uploads/3/1/7/9/3179747/wbsc03-zagheni.pdf

Inferring international and internal migration patterns from Twitter data

The increasing ubiquity of Internet use has opened up new avenues in the study of human mobility. Easily-obtainable geolocation data resulting from repeated logins to the same website offer the possibility of observing long-term patterns of mobility for a large number of individuals. We use data on the geographic locations from where over 100 million anonymized users log into Yahoo!~services to generate the first global map of short- and medium-term mobility flows. We develop a protocol to identify anonymized users who, over a one-year period, had spent more than 3 months in a different country from their stated country of residence ("migrants"), and users who spent less than a month in another country ("tourists"). We compute aggregate estimates of migration propensities between countries, as inferred from a user's location over the observed period. Geolocation data allow us to characterize also the pendularity of migration flows -- i.e., the extent to which migrants travel back and forth between their countries of origin and destination. We use data regarding visa regimes, colonial ties, geographic location and economic development to predict migration and tourism flows. Our analysis shows the persistence of traditional migration patterns as well as the emergence of new routes. Migrations tend to be more pendular between countries that are close to each other. We observe particularly high levels of pendularity within the European Economic Area, even after we control for distance and visa regimes. The dataset, methodology and results presented have important implications for the travel industry, as well as for several disciplines in social sciences, including geography, demography and the sociology of networks.

/pdf/studying-inter-national-mobility-through-ip-geolocation-g3v729kah1.pdf

Studying inter-national mobility through IP geolocation

We investigate trends in the international migration of professional workers by analyzing a dataset of millions of geolocated career histories provided by LinkedIn, the largest online platform for professionals. The new dataset confirms that the United States is, in absolute terms, the top destination for international migrants. However, we observe a decrease, from 2000 to 2012, in the percentage of professional migrants, worldwide, who have the United States as their country of destination. The pattern holds for persons with Bachelor’s, Master’s, and PhD degrees alike, and for individuals with degrees from highly-ranked worldwide universities. Our analysis also reveals the growth of Asia as a major professional migration destination during the past twelve years. Although we see a decline in the share of employment-based migrants going to the United States, our results show a recent rebound in the percentage of international students who choose the United States as their destination.

/pdf/migration-of-professionals-to-the-u-s-evidence-from-linkedin-25u27muwlg.pdf

Migration of Professionals to the U.S. Evidence from LinkedIn data

We explore the impact of technology on the strength of friendship ties. Data come from about two millions ties that members of CouchSurfing—an international hospitality organization whose goal is to promote travelling and friendship between its members—developed between 2003 and 2011 as well as original and secondary ethnographic data. The community, and the data available about its members, grew exponentially during our period of analysis, yet friendships between users tended to be stronger in the early years of CouchSurfing, when the online reputation system was still developing and the whole network was enmeshed in considerable uncertainty. We argue that this case illustrates a process of disenchantment created by technology, where technology increases the ease with which we form friendships around common cultural interests and, at the same time, diminishes the bonding power of these experiences.

Disenchanting the World: The Impact of Technology on Relationships

Conflicts fueled by popular religious mobilization have rekindled the controversy surrounding Samuel Huntington’s theory of changing international alignments in the Post-Cold War era. In The Clash of Civilizations, Huntington challenged Fukuyama’s “end of history” thesis that liberal democracy had emerged victorious out of Post-war ideological and economic rivalries. Based on a top-down analysis of the alignments of nation states, Huntington famously concluded that the axes of international geo-political conflicts had reverted to the ancient cultural divisions that had characterized most of human history. Until recently, however, the debate has had to rely more on polemics than empirical evidence. Moreover, Huntington made this prediction in 1993, before social media connected the world’s population. Do digital communications attenuate or echo the cultural, religious, and ethnic “fault lines” posited by Huntington prior to the global diffusion of social media? We revisit Huntington's thesis using hundreds of millions of anonymized email and Twitter communications among tens of millions of worldwide users to map the global alignment of interpersonal relations. Contrary to the supposedly borderless world of cyberspace, a bottom-up analysis confirms the persistence of the eight culturally differentiated civilizations posited by Huntington, with the divisions corresponding to differences in language, religion, economic development, and spatial distance.

/pdf/the-mesh-of-civilizations-in-the-global-network-of-digital-1m2suactmh.pdf

Bogdan State

Papers

Inferring international and internal migration patterns from Twitter data

Studying inter-national mobility through IP geolocation

Migration of Professionals to the U.S. Evidence from LinkedIn data

Disenchanting the World: The Impact of Technology on Relationships

The mesh of civilizations in the global network of digital communication.