  We consider the effects of the global financial crisis through a local Korean
financial market around the 2008 crisis. We analyze 185 individual stock prices
belonging to the KOSPI (Korea Composite Stock Price Index), cosidering three
time periods: the time before, during, and after the crisis. The complex
networks generate from the fully connected correlation network by using the
cross-correlation coefficients among the stock price time series of the
companies. We generate the threshold networks (TN), the minimal spanning tees
(MST), and the hierarchical network (HN) from the fully connected
cross-correlation networks. By assigning a threshold value of the
cross-correlation coefficient, we obtain the threshold networks. We observe the
power law of the degree distribution in the limited range of the threshold. The
degree distribution of the largest cluster in the threshold networks during the
crisis is fatter than other periods. The clustering coefficient of the
threshold networks follows the power law in the scaling range. We also generate
the minimal spanning trees from the fully connected correlation networks. The
MST during the crisis period shrinks in comparison to the periods before and
after the crisis. The cophenetic correlation coefficient increases during the
crisis, indicating that the hierarchical structure increases during this
period. When the crisis hit the market, the companies behave synchronously and
their correlations become stronger than the normal period.
