This study investigates volatility spillovers and network connectedness among four cryptocurrencies (Bitcoin, Ethereum, Tether, and BNB coin), four energy companies (Exxon Mobil, Chevron, ConocoPhillips, and Nextera Energy), and four mega-technology companies (Apple, Microsoft, Alphabet, and Amazon) in the US. We analyze data for the period November 15, 2017–October 28, 2022 using methodologies in Diebold and Yilmaz (Int J Forecast 28(1):57–66, 2012) and Baruník and Křehlík (J Financ Economet 16(2):271–296 2018). Our analysis shows the COVID-19 pandemic amplified volatility spillovers, thereby intensifying the impact of financial contagion between markets. This finding indicates the impact of the pandemic on the US economy heightened risk transmission across markets. Moreover, we show that Bitcoin, Ethereum, Chevron, ConocoPhilips, Apple, and Microsoft are net volatility transmitters, while Tether, BNB, Exxon Mobil, Nextera Energy, Alphabet, and Amazon are net receivers Our results suggest that short-term volatility spillovers outweigh medium- and long-term spillovers, and that investors should be more concerned about short-term repercussions because they do not have enough time to act quickly to protect themselves from market risks when the US market is affected. Furthermore, in contrast to short-term dynamics, longer term patterns display superior hedging efficiency. The net-pairwise directional spillovers show that Alphabet and Amazon are the highest shock transmitters to other companies. The findings in this study have implications for both investors and policymakers.

中文翻译：

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领先的加密货币与美国能源和科技公司之间的波动溢出

本研究调查了四种加密货币（比特币、以太坊、Tether 和 BNB 币）、四家能源公司（埃克森美孚、雪佛龙、康菲石油公司和 Nextera Energy）和四家大型科技公司（苹果、微软、 Alphabet 和亚马逊）在美国。我们使用 Diebold 和 Yilmaz (Int J Forecast 28(1):57–66, 2012) 以及 Baruník 和 Křehlík (J Financ Economet 16(2):271) 的方法分析了 2017 年 11 月 15 日至 2022 年 10 月 28 日期间的数据。 –296 2018）。我们的分析显示，COVID-19 大流行加剧了波动性溢出效应，从而加剧了市场之间金融传染的影响。这一发现表明，疫情对美国经济的影响加剧了市场间的风险传导。此外，我们还发现，比特币、以太坊、雪佛龙、康菲公司、苹果和微软是净波动性传播者，而 Tether、BNB、埃克森美孚、Nextera Energy、Alphabet 和亚马逊是净波动性接收者。我们的结果表明，短期波动性溢出效应大于中长期溢出效应，投资者应该更关注短期影响，因为当美国市场受到影响时，他们没有足够的时间迅速采取行动保护自己免受市场风险的影响。此外，与短期动态相比，长期模式显示出卓越的对冲效率。净成对的定向溢出表明，Alphabet 和亚马逊是对其他公司的最大冲击传递者。这项研究的结果对投资者和政策制定者都有影响。