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The role of uncertainty and sentiment for intraday volatility connectedness between oil and financial markets

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  • Szafranek, Karol
  • Rubaszek, Michał
  • Uddin, Gazi Salah

Abstract

We quantify intraday volatility connectedness between oil and key financial assets and assess how it is related to uncertainty and sentiment measures. For that purpose, we integrate the well-known spillover methodology with a TVP VAR model estimated on a unique, vast dataset of roughly 300 thousand 5 min quotations for most heavily traded financial assets: crude oil, the US dollar, S&P 500 index, gold and US treasury bonds. This distinguishes our investigation from previous studies, which usually employ relatively short samples of daily or weekly data and focus on connectedness between two asset classes. We contribute to the literature across three margins. First, we document that market connectedness at intraday frequency presents a different picture on markets co-movement compared to the estimates obtained using daily data. Second, we show that at 5 min frequency volatility is mostly transmitted from the stock market and absorbed by the bond and dollar markets, with oil and gold markets being occasionally important for volatility transmission. Third, we present evidence that daily averages of intraday connectedness measures respond to changes in sentiment and market-specific uncertainty. Interestingly, our results contrast with earlier findings, as they show that connectedness among markets decreases in periods of high volatility owing to market-specific factors. Our study points to the importance of using high-frequency data in order to better understand financial and commodity markets dynamics.

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  • Szafranek, Karol & Rubaszek, Michał & Uddin, Gazi Salah, 2024. "The role of uncertainty and sentiment for intraday volatility connectedness between oil and financial markets," Energy Economics, Elsevier, vol. 137(C).
  • Handle: RePEc:eee:eneeco:v:137:y:2024:i:c:s0140988324004687
    DOI: 10.1016/j.eneco.2024.107760
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    1. Narayan, Paresh Kumar & Narayan, Seema & Zheng, Xinwei, 2010. "Gold and oil futures markets: Are markets efficient?," Applied Energy, Elsevier, vol. 87(10), pages 3299-3303, October.
    2. Diebold, Francis X. & Yılmaz, Kamil, 2014. "On the network topology of variance decompositions: Measuring the connectedness of financial firms," Journal of Econometrics, Elsevier, vol. 182(1), pages 119-134.
    3. Andres Algaba & David Ardia & Keven Bluteau & Samuel Borms & Kris Boudt, 2020. "Econometrics Meets Sentiment: An Overview Of Methodology And Applications," Journal of Economic Surveys, Wiley Blackwell, vol. 34(3), pages 512-547, July.
    4. Śmiech, Sławomir & Papież, Monika & Rubaszek, Michał & Snarska, Małgorzata, 2021. "The role of oil price uncertainty shocks on oil-exporting countries," Energy Economics, Elsevier, vol. 93(C).
    5. Antonakakis, Nikolaos & Gupta, Rangan & Kollias, Christos & Papadamou, Stephanos, 2017. "Geopolitical risks and the oil-stock nexus over 1899–2016," Finance Research Letters, Elsevier, vol. 23(C), pages 165-173.
    6. Benlagha, Noureddine & Karim, Sitara & Naeem, Muhammad Abubakr & Lucey, Brian M. & Vigne, Samuel A., 2022. "Risk connectedness between energy and stock markets: Evidence from oil importing and exporting countries," Energy Economics, Elsevier, vol. 115(C).
    7. Yu-Chin Chen & Kenneth S. Rogoff & Barbara Rossi, 2010. "Can Exchange Rates Forecast Commodity Prices?," The Quarterly Journal of Economics, President and Fellows of Harvard College, vol. 125(3), pages 1145-1194.
    8. Kang, Wensheng & Ratti, Ronald A. & Yoon, Kyung Hwan, 2014. "The impact of oil price shocks on U.S. bond market returns," Energy Economics, Elsevier, vol. 44(C), pages 248-258.
    9. Dario Caldara & Matteo Iacoviello, 2022. "Measuring Geopolitical Risk," American Economic Review, American Economic Association, vol. 112(4), pages 1194-1225, April.
    10. Lubos Pástor & Pietro Veronesi, 2012. "Uncertainty about Government Policy and Stock Prices," Journal of Finance, American Finance Association, vol. 67(4), pages 1219-1264, August.
    11. Malik, Farooq & Umar, Zaghum, 2019. "Dynamic connectedness of oil price shocks and exchange rates," Energy Economics, Elsevier, vol. 84(C).
    12. Adekoya, Oluwasegun B. & Oliyide, Johnson A., 2021. "How COVID-19 drives connectedness among commodity and financial markets: Evidence from TVP-VAR and causality-in-quantiles techniques," Resources Policy, Elsevier, vol. 70(C).
    13. Aktham Maghyereh & Hussein Abdoh, 2022. "COVID-19 and the volatility interlinkage between bitcoin and financial assets," Empirical Economics, Springer, vol. 63(6), pages 2875-2901, December.
    14. Ben S. Bernanke, 1983. "Irreversibility, Uncertainty, and Cyclical Investment," The Quarterly Journal of Economics, President and Fellows of Harvard College, vol. 98(1), pages 85-106.
    15. Theo S. Eicher & Chris Papageorgiou & Adrian E. Raftery, 2011. "Default priors and predictive performance in Bayesian model averaging, with application to growth determinants," Journal of Applied Econometrics, John Wiley & Sons, Ltd., vol. 26(1), pages 30-55, January/F.
    16. Corbet, Shaen & Goodell, John W. & Günay, Samet, 2020. "Co-movements and spillovers of oil and renewable firms under extreme conditions: New evidence from negative WTI prices during COVID-19," Energy Economics, Elsevier, vol. 92(C).
    17. Peng, Cheng & Zhu, Huiming & Guo, Yawei & Chen, Xiuyun, 2018. "Risk spillover of international crude oil to China's firms: Evidence from granger causality across quantile," Energy Economics, Elsevier, vol. 72(C), pages 188-199.
    18. Nazlioglu, Saban & Gupta, Rangan & Bouri, Elie, 2020. "Movements in international bond markets: The role of oil prices," International Review of Economics & Finance, Elsevier, vol. 68(C), pages 47-58.
    19. Koop, Gary & Pesaran, M. Hashem & Potter, Simon M., 1996. "Impulse response analysis in nonlinear multivariate models," Journal of Econometrics, Elsevier, vol. 74(1), pages 119-147, September.
    20. Fernandez, Carmen & Ley, Eduardo & Steel, Mark F. J., 2001. "Benchmark priors for Bayesian model averaging," Journal of Econometrics, Elsevier, vol. 100(2), pages 381-427, February.
    21. Awartani, Basel & Maghyereh, Aktham Issa, 2013. "Dynamic spillovers between oil and stock markets in the Gulf Cooperation Council Countries," Energy Economics, Elsevier, vol. 36(C), pages 28-42.
    22. Koop, Gary & Korobilis, Dimitris, 2014. "A new index of financial conditions," European Economic Review, Elsevier, vol. 71(C), pages 101-116.
    23. Pesaran, H. Hashem & Shin, Yongcheol, 1998. "Generalized impulse response analysis in linear multivariate models," Economics Letters, Elsevier, vol. 58(1), pages 17-29, January.
    24. Cui, Jinxin & Maghyereh, Aktham, 2023. "Higher-order moment risk connectedness and optimal investment strategies between international oil and commodity futures markets: Insights from the COVID-19 pandemic and Russia-Ukraine conflict," International Review of Financial Analysis, Elsevier, vol. 86(C).
    25. Awartani, Basel & Aktham, Maghyereh & Cherif, Guermat, 2016. "The connectedness between crude oil and financial markets: Evidence from implied volatility indices," Journal of Commodity Markets, Elsevier, vol. 4(1), pages 56-69.
    26. Giorgio E. Primiceri, 2005. "Time Varying Structural Vector Autoregressions and Monetary Policy," The Review of Economic Studies, Review of Economic Studies Ltd, vol. 72(3), pages 821-852.
    27. Dąbrowski, Marek A. & Papież, Monika & Rubaszek, Michał & Śmiech, Sławomir, 2022. "The role of economic development for the effect of oil market shocks on oil-exporting countries. Evidence from the interacted panel VAR model," Energy Economics, Elsevier, vol. 110(C).
    28. Koop, Gary & Korobilis, Dimitris, 2013. "Large time-varying parameter VARs," Journal of Econometrics, Elsevier, vol. 177(2), pages 185-198.
    29. Zhang, Yue-Jun & Wei, Yi-Ming, 2010. "The crude oil market and the gold market: Evidence for cointegration, causality and price discovery," Resources Policy, Elsevier, vol. 35(3), pages 168-177, September.
    30. Wiggins, Seth & Etienne, Xiaoli L., 2017. "Turbulent times: Uncovering the origins of US natural gas price fluctuations since deregulation," Energy Economics, Elsevier, vol. 64(C), pages 196-205.
    31. Okhrin, Yarema & Uddin, Gazi Salah & Yahya, Muhammad, 2023. "Nonlinear and asymmetric interconnectedness of crude oil with financial and commodity markets," Energy Economics, Elsevier, vol. 125(C).
    32. Luo, Jiawen & Ji, Qiang, 2018. "High-frequency volatility connectedness between the US crude oil market and China's agricultural commodity markets," Energy Economics, Elsevier, vol. 76(C), pages 424-438.
    33. Balcilar, Mehmet & Gupta, Rangan & Wang, Shixuan & Wohar, Mark E., 2020. "Oil price uncertainty and movements in the US government bond risk premia," The North American Journal of Economics and Finance, Elsevier, vol. 52(C).
    34. Antonakakis, Nikolaos & Cunado, Juncal & Filis, George & Gabauer, David & Perez de Gracia, Fernando, 2018. "Oil volatility, oil and gas firms and portfolio diversification," Energy Economics, Elsevier, vol. 70(C), pages 499-515.
    35. Phan, Dinh Hoang Bach & Sharma, Susan Sunila & Narayan, Paresh Kumar, 2016. "Intraday volatility interaction between the crude oil and equity markets," Journal of International Financial Markets, Institutions and Money, Elsevier, vol. 40(C), pages 1-13.
    36. Oguzhan Ozcelebi & Kaya Tokmakcioglu, 2022. "Assessment of the asymmetric impacts of the geopolitical risk on oil market dynamics," International Journal of Finance & Economics, John Wiley & Sons, Ltd., vol. 27(1), pages 275-289, January.
    37. Umar, Zaghum & Abrar, Afsheen & Hadhri, Sinda & Sokolova, Tatiana, 2023. "The connectedness of oil shocks, green bonds, sukuks and conventional bonds," Energy Economics, Elsevier, vol. 119(C).
    38. Akyildirim, Erdinc & Cepni, Oguzhan & Molnár, Peter & Uddin, Gazi Salah, 2022. "Connectedness of energy markets around the world during the COVID-19 pandemic," Energy Economics, Elsevier, vol. 109(C).
    39. Adekoya, Oluwasegun B. & Oliyide, Johnson A. & Yaya, OlaOluwa S. & Al-Faryan, Mamdouh Abdulaziz Saleh, 2022. "Does oil connect differently with prominent assets during war? Analysis of intra-day data during the Russia-Ukraine saga," Resources Policy, Elsevier, vol. 77(C).
    40. Enrique Moral‐Benito, 2016. "Growth Empirics in Panel Data Under Model Uncertainty and Weak Exogeneity," Journal of Applied Econometrics, John Wiley & Sons, Ltd., vol. 31(3), pages 584-602, April.
    41. Husain, Shaiara & Tiwari, Aviral Kumar & Sohag, Kazi & Shahbaz, Muhammad, 2019. "Connectedness among crude oil prices, stock index and metal prices: An application of network approach in the USA," Resources Policy, Elsevier, vol. 62(C), pages 57-65.
    42. Mensi, Walid & Ali, Syed Riaz Mahmood & Vo, Xuan Vinh & Kang, Sang Hoon, 2022. "Multiscale dependence, spillovers, and connectedness between precious metals and currency markets: A hedge and safe-haven analysis," Resources Policy, Elsevier, vol. 77(C).
    43. Mensi, Walid & Vo, Xuan Vinh & Kang, Sang Hoon, 2022. "COVID-19 pandemic’s impact on intraday volatility spillover between oil, gold, and stock markets," Economic Analysis and Policy, Elsevier, vol. 74(C), pages 702-715.
    44. Dai, Zhifeng & Kang, Jie, 2021. "Bond yield and crude oil prices predictability," Energy Economics, Elsevier, vol. 97(C).
    45. Szafranek, Karol & Papież, Monika & Rubaszek, Michał & Śmiech, Sławomir, 2023. "How immune is the connectedness of European natural gas markets to exceptional shocks?," Resources Policy, Elsevier, vol. 85(PA).
    46. Diebold, Francis X. & Yilmaz, Kamil, 2012. "Better to give than to receive: Predictive directional measurement of volatility spillovers," International Journal of Forecasting, Elsevier, vol. 28(1), pages 57-66.
    47. Rehman, Mobeen Ur & Shahzad, Syed Jawad Hussain & Uddin, Gazi Salah & Hedström, Axel, 2018. "Precious metal returns and oil shocks: A time varying connectedness approach," Resources Policy, Elsevier, vol. 58(C), pages 77-89.
    48. Ruzhao Gao & Yancai Zhao & Bing Zhang, 2021. "The spillover effects of economic policy uncertainty on the oil, gold, and stock markets: Evidence from China," International Journal of Finance & Economics, John Wiley & Sons, Ltd., vol. 26(2), pages 2134-2141, April.
    49. Karol Szafranek & Marek Kwas & Grzegorz Szafrański & Zuzanna Wośko, 2020. "Common Determinants of Credit Default Swap Premia in the North American Oil and Gas Industry. A Panel BMA Approach," Energies, MDPI, vol. 13(23), pages 1-23, November.
    50. Umar, Zaghum & Aharon, David Y. & Esparcia, Carlos & AlWahedi, Wafa, 2022. "Spillovers between sovereign yield curve components and oil price shocks," Energy Economics, Elsevier, vol. 109(C).
    51. Nikolaos Antonakakis & Ioannis Chatziantoniou & David Gabauer, 2020. "Refined Measures of Dynamic Connectedness based on Time-Varying Parameter Vector Autoregressions," JRFM, MDPI, vol. 13(4), pages 1-23, April.
    52. Xavier Sala-I-Martin & Gernot Doppelhofer & Ronald I. Miller, 2004. "Determinants of Long-Term Growth: A Bayesian Averaging of Classical Estimates (BACE) Approach," American Economic Review, American Economic Association, vol. 94(4), pages 813-835, September.
    53. Bilgin, Mehmet Huseyin & Gozgor, Giray & Lau, Chi Keung Marco & Sheng, Xin, 2018. "The effects of uncertainty measures on the price of gold," International Review of Financial Analysis, Elsevier, vol. 58(C), pages 1-7.
    54. Sharif, Arshian & Aloui, Chaker & Yarovaya, Larisa, 2020. "COVID-19 pandemic, oil prices, stock market, geopolitical risk and policy uncertainty nexus in the US economy: Fresh evidence from the wavelet-based approach," International Review of Financial Analysis, Elsevier, vol. 70(C).
    55. Zhang, Hongwei & Demirer, Riza & Huang, Jianbai & Huang, Wanjun & Tahir Suleman, Muhammad, 2021. "Economic policy uncertainty and gold return dynamics: Evidence from high-frequency data," Resources Policy, Elsevier, vol. 72(C).
    56. Bouri, Elie & Lei, Xiaojie & Jalkh, Naji & Xu, Yahua & Zhang, Hongwei, 2021. "Spillovers in higher moments and jumps across US stock and strategic commodity markets," Resources Policy, Elsevier, vol. 72(C).
    57. Farid, Saqib & Kayani, Ghulam Mujtaba & Naeem, Muhammad Abubakr & Shahzad, Syed Jawad Hussain, 2021. "Intraday volatility transmission among precious metals, energy and stocks during the COVID-19 pandemic," Resources Policy, Elsevier, vol. 72(C).
    58. Zhang, Dayong, 2017. "Oil shocks and stock markets revisited: Measuring connectedness from a global perspective," Energy Economics, Elsevier, vol. 62(C), pages 323-333.
    59. Gormus, Alper & Nazlioglu, Saban & Soytas, Ugur, 2018. "High-yield bond and energy markets," Energy Economics, Elsevier, vol. 69(C), pages 101-110.
    60. Gong, Xu & Xu, Jun, 2022. "Geopolitical risk and dynamic connectedness between commodity markets," Energy Economics, Elsevier, vol. 110(C).
    61. Maghyereh, Aktham I. & Awartani, Basel & Bouri, Elie, 2016. "The directional volatility connectedness between crude oil and equity markets: New evidence from implied volatility indexes," Energy Economics, Elsevier, vol. 57(C), pages 78-93.
    62. Naeem, Muhammad Abubakr & Karim, Sitara & Yarovaya, Larisa & Lucey, Brian M., 2023. "COVID-induced sentiment and the intraday volatility spillovers between energy and other ETFs," Energy Economics, Elsevier, vol. 122(C).
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    More about this item

    Keywords

    Volatility connectedness; Uncertainty and sentiment; Oil market; Intraday data; TVP VAR model;
    All these keywords.

    JEL classification:

    • C32 - Mathematical and Quantitative Methods - - Multiple or Simultaneous Equation Models; Multiple Variables - - - Time-Series Models; Dynamic Quantile Regressions; Dynamic Treatment Effect Models; Diffusion Processes; State Space Models
    • C58 - Mathematical and Quantitative Methods - - Econometric Modeling - - - Financial Econometrics
    • D80 - Microeconomics - - Information, Knowledge, and Uncertainty - - - General
    • G15 - Financial Economics - - General Financial Markets - - - International Financial Markets
    • Q41 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Energy - - - Demand and Supply; Prices

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