Özet:

In this study, Minimum Spanning Tree (MST) analysis was carried out on how the Covid-19 pandemic changed the relationships between BIST100 companies. The aim of the study is to distinguish the permanent and temporary effects of the relations and hierarchical interactions between BIST100 companies of the pandemic. According to the results of the MST analysis, the effect of the correlation network that emerged in three periods as before, during and after the pandemic on company returns and the financial impact of policy signals were discussed. With the pandemic, an increase was observed in the sectoral clustering of companies. Companies that are in the position of core stocks in terms of being most connected with other stocks have lost their positions with the pandemic. The banking and finance sector has gained a significant weight in the interaction network between companies. To analyze how portfolio diversification was affected by the pandemic, a portfolio was created using MST's centrality measures and beta coefficients, and the portfolio's risks and returns were calculated for all three sub-periods. The Covid-19 pandemic has increased the risk of the portfolio consisting of companies that are least connected to the market and other companies due to the change in the correlation network between companies, reducing the potential benefit of portfolio diversification.

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