  We investigate the structure of global inter-firm linkages using a dataset
that contains information on business partners for about 400,000 firms
worldwide, including all the firms listed on the major stock exchanges. Among
the firms, we examine three networks, which are based on customer-supplier,
licensee-licensor, and strategic alliance relationships. First, we show that
these networks all have scale-free topology and that the degree distribution
for each follows a power law with an exponent of 1.5. The shortest path length
is around six for all three networks. Second, we show through community
structure analysis that the firms comprise a community with those firms that
belong to the same industry but different home countries, indicating the
globalization of firms' production activities. Finally, we discuss what such
production globalization implies for the proliferation of conflict minerals
(i.e., minerals extracted from conflict zones and sold to firms in other
countries to perpetuate fighting) through global buyer-supplier linkages. We
show that a limited number of firms belonging to some specific industries and
countries plays an important role in the global proliferation of conflict
minerals. Our numerical simulation shows that regulations on the purchases of
conflict minerals by those firms would substantially reduce their worldwide
use.
