University of Mannheim

About: University of Mannheim is a education organization based out in Mannheim, Germany. It is known for research contribution in the topics: Population & European union. The organization has 4448 authors who have published 12918 publications receiving 446557 citations. The organization is also known as: Uni Mannheim & UMA.

Graph structure in the web --- revisited: a trick of the heavy tail

Abstract: Knowledge about the general graph structure of the World Wide Web is important for understanding the social mechanisms that govern its growth, for designing ranking methods, for devising better crawling algorithms, and for creating accurate models of its structure. In this paper, we describe and analyse a large, publicly accessible crawl of the web that was gathered by the Common Crawl Foundation in 2012 and that contains over 3.5 billion web pages and 128.7 billion links. This crawl makes it possible to observe the evolution of the underlying structure of the World Wide Web within the last 10 years: we analyse and compare, among other features, degree distributions, connectivity, average distances, and the structure of weakly/strongly connected components. Our analysis shows that, as evidenced by previous research, some of the features previously observed by Broder et al. are very dependent on artefacts of the crawling process, whereas other appear to be more structural. We confirm the existence of a giant strongly connected component; we however find, as observed by other researchers, very different proportions of nodes that can reach or that can be reached from the giant component, suggesting that the "bow-tie structure" is strongly dependent on the crawling process, and to the best of our current knowledge is not a structural property of the web. More importantly, statistical testing and visual inspection of size-rank plots show that the distributions of indegree, outdegree and sizes of strongly connected components are not power laws, contrarily to what was previously reported for much smaller crawls, although they might be heavy-tailed. We also provide for the first time accurate measurement of distance-based features, using recently introduced algorithms that scale to the size of our crawl.

Testing for uniform wage trends in West-Germany: A cohort analysis using quantile regressions for censored data

Abstract: The rise of unemployment in West Germany is often attributed to an inflexibility of the wage structure in the face of a skill bias in labor demand trends. In addition, there is concern in Germany that during the 70s and 80s unions were pursuing a too egalitarian wage policy. In a cohort analysis, we estimate quantile regressions of wages taking account of the censoring in the data. We present a new framework to describe trends in the entire wage distribution across education and age groups in a parsimonious way. We explore whether wage trends are uniform across cohorts, thus defining a macroeconomic wage trend. Our findings are that wages of workers with intermediate education levels, among them especially those of young workers, deteriorated slightly relative to both high and low education levels. Wage inequality within age-education groups stayed fairly constant. Nevertheless, the German wage structure was fairly stable, especially in international comparison. The results appear consistent with a skill bias in labor demand trends, recognizing that union wages are only likely to be binding floors for low-wage earners.