Comparison of Complex Networks of Stock Markets and Economic Variables in the Period Before and After the Outbreak of Coronavirus (Covid-19)

The corona virus has turned a health crisis into an economic crisis and its spread has led to strong negative reactions from stock markets in various countries and price fluctuations in many macroeconomic variables. On the other hand, the spread of the virus provides a basis for examining the effects of its prevalence on stock markets, economic variables and the power of influence and the speed of information dissemination in times of crisis in these markets. The aim of the present study was to investigate the effect of corona virus on the stock markets of 75 countries and the variables of oil, gold, silver and copper by comparing complex networks before and after the outbreak of the virus. Also, for the calculation section, matlab statistical software has been used and for drawing the networks, the maximum filtered flat graph method has been used with the help of daily data in the period from June 2019 to March 2020. the results show that before the outbreak of coronavirus, stock markets tended to move in small continental groups, but the outbreak of the virus led to negative group movements with high correlation for these markets, positive or negative information spreads 32% faster than before on the stock market network, also stock markets are twice as influential as they were before the outbreak. The corona virus has directly led to a 40% drop in stock markets. on the other hand, the virus has caused fluctuations in the global variables of oil, gold, silver and copper, which each respectively affected 55%, 32%, 28% and 35% of stock markets, the impact of these variables before the outbreak of the virus was 31%, 20%, 16% and 18% of stock markets, respectively.‌ it is important to note that in crises due to the collective movements of stock markets, price stability in central stock markets and macroeconomic variables are very important to control and reduce the negative effects of the crisis on stock markets.