  This work uses the stocks of the 197 largest companies in the world, in terms
of market capitalization, in the financial area in the study of causal
relationships between them using Transfer Entropy, which is calculated using
the stocks of those companies and their counterparts lagged by one day. With
this, we can assess which companies influence others according to sub-areas of
the financial sector, which are banks, diversified financial services, savings
and loans, insurance, private equity funds, real estate investment companies,
and real estate trust funds. We also analyzed the causality relations between
those stocks and the network formed by them based on this measure, verifying
that they cluster mainly according to countries of origin, and then by industry
and sub-industry. Then we collected data on the stocks of companies in the
financial sector of some countries that are suffering the most with the current
credit crisis: Greece, Cyprus, Ireland, Spain, Portugal, and Italy, and assess,
also using transfer entropy, which companies from the largest 197 are most
affected by the stocks of these countries in crisis. The intention is to map a
network of influences that may be used in the study of possible contagions
originating in those countries in financial crisis.
