139 research outputs found
Visualizing a large-scale structure of production network by N-body simulation
Our recent study of a nation-wide production network uncovered a community
structure, namely how firms are connected by supplier-customer links into
tightly-knit groups with high density in intra-groups and with lower
connectivity in inter-groups. Here we propose a method to visualize the
community structure by a graph layout based on a physical analogy. The layout
can be calculated in a practical computation-time and is possible to be
accelerated by a special-purpose device of GRAPE (gravity pipeline) developed
for astrophysical N-body simulation. We show that the method successfully
identifies the communities in a hierarchical way by applying it to the
manufacturing sector comprising tenth million nodes and a half million edges.
In addition, we discuss several limitations of this method, and propose a
possible way to avoid all those problems
Shareholding Networks in Japan
The Japanese shareholding network existing at the end of March 2002 is
studied empirically. The network is constructed from 2,303 listed companies and
53 non-listed financial institutions. We consider this network as a directed
graph by drawing edges from shareholders to stock corporations. The lengths of
the shareholder lists vary with the companies, and the most comprehensive lists
contain the top 30 shareholders. Consequently, the distribution of incoming
edges has an upper bound, while that of outgoing edges has no bound. The
distribution of outgoing degrees is well explained by the power law function
with an exponential tail. The exponent in the power law range is gamma=1.7. To
understand these features from the viewpoint of a company's growth, we consider
the correlations between the outgoing degree and the company's age, profit, and
total assets.Comment: 10 pages, 4 figures, International Conference Science of Complex
Networks: from Biology to the Internet and WWW (CNET2004
Labour Productivity Superstatistics
We discuss superstatistics theory of labour productivity. Productivity
distribution across workers, firms and industrial sectors are studied
empirically and found to obey power-distributions, in sharp contrast to the
equilibrium theories of mainstream economics. The Pareto index is found to
decrease with the level of aggregation, {\it i.e.}, from workers to firms and
to industrial sectors. In order to explain these phenomenological laws, we
propose a superstatistics framework, where the role of the fluctuating
temperature is played by the fluctuating demand.Comment: 13 pages including figure
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