IDEAS home Printed from https://ideas.repec.org/a/eee/eneeco/v109y2022ics0140988322001281.html
   My bibliography  Save this article

A clean, green haven?—Examining the relationship between clean energy, clean and dirty cryptocurrencies

Author

Listed:
  • Ren, Boru
  • Lucey, Brian

Abstract

Is clean energy a safe haven for cryptocurrencies, or vice versa? In this paper, we investigate the hedge and safe haven property of a wide range of clean energy indices against two distinct types of cryptocurrencies based on their energy consumption levels, termed “dirty” and “clean”. Statistical evidence shows that clean energy is not a direct hedge for either of types. However, it serves as at least a weak safe haven for both in extreme bearish markets. Moreover, clean energy is more likely to be a safe haven for dirty cryptocurrencies than clean cryptocurrencies during increased uncertainty. We further study the spillover patterns among clean energy, cryptocurrency, stock, and gold markets. Weak connectedness is found between clean energy and cryptocurrencies which implies the potential use of clean energy as a hedge and diversification tool for cryptocurrencies in the future.

Suggested Citation

  • Ren, Boru & Lucey, Brian, 2022. "A clean, green haven?—Examining the relationship between clean energy, clean and dirty cryptocurrencies," Energy Economics, Elsevier, vol. 109(C).
  • Handle: RePEc:eee:eneeco:v:109:y:2022:i:c:s0140988322001281
    DOI: 10.1016/j.eneco.2022.105951
    as

    Download full text from publisher

    File URL: http://www.sciencedirect.com/science/article/pii/S0140988322001281
    Download Restriction: Full text for ScienceDirect subscribers only

    File URL: https://libkey.io/10.1016/j.eneco.2022.105951?utm_source=ideas
    LibKey link: if access is restricted and if your library uses this service, LibKey will redirect you to where you can use your library subscription to access this item
    ---><---

    As the access to this document is restricted, you may want to search for a different version of it.

    References listed on IDEAS

    as
    1. Le, Lan-TN & Yarovaya, Larisa & Nasir, Muhammad Ali, 2021. "Did COVID-19 change spillover patterns between Fintech and other asset classes?," Research in International Business and Finance, Elsevier, vol. 58(C).
    2. Le, TN-Lan & Abakah, Emmanuel Joel Aikins & Tiwari, Aviral Kumar, 2021. "Time and frequency domain connectedness and spill-over among fintech, green bonds and cryptocurrencies in the age of the fourth industrial revolution," Technological Forecasting and Social Change, Elsevier, vol. 162(C).
    3. Maghyereh, Aktham & Abdoh, Hussein, 2020. "Tail dependence between Bitcoin and financial assets: Evidence from a quantile cross-spectral approach," International Review of Financial Analysis, Elsevier, vol. 71(C).
    4. 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.
    5. Baur, Dirk G. & McDermott, Thomas K., 2010. "Is gold a safe haven? International evidence," Journal of Banking & Finance, Elsevier, vol. 34(8), pages 1886-1898, August.
    6. Saeed, Tareq & Bouri, Elie & Alsulami, Hamed, 2021. "Extreme return connectedness and its determinants between clean/green and dirty energy investments," Energy Economics, Elsevier, vol. 96(C).
    7. Uzonwanne, Godfrey, 2021. "Volatility and return spillovers between stock markets and cryptocurrencies," The Quarterly Review of Economics and Finance, Elsevier, vol. 82(C), pages 30-36.
    8. Dirk G. Baur & Brian M. Lucey, 2010. "Is Gold a Hedge or a Safe Haven? An Analysis of Stocks, Bonds and Gold," The Financial Review, Eastern Finance Association, vol. 45(2), pages 217-229, May.
    9. Schinckus, Christophe, 2021. "Proof-of-work based blockchain technology and Anthropocene: An undermined situation?," Renewable and Sustainable Energy Reviews, Elsevier, vol. 152(C).
    10. Jiang, Shangrong & Li, Yuze & Lu, Quanying & Wang, Shouyang & Wei, Yunjie, 2022. "Volatility communicator or receiver? Investigating volatility spillover mechanisms among Bitcoin and other financial markets," Research in International Business and Finance, Elsevier, vol. 59(C).
    11. Umar, Zaghum & Trabelsi, Nader & Alqahtani, Faisal, 2021. "Connectedness between cryptocurrency and technology sectors: International evidence," International Review of Economics & Finance, Elsevier, vol. 71(C), pages 910-922.
    12. Elie Bouri & Mahamitra Das & Rangan Gupta & David Roubaud, 2018. "Spillovers between Bitcoin and other assets during bear and bull markets," Applied Economics, Taylor & Francis Journals, vol. 50(55), pages 5935-5949, November.
    13. Wasim Ahmad & Shirin Rais, 2018. "Time-Varying Spillover and the Portfolio Diversification Implications of Clean Energy Equity with Commodities and Financial Assets," Emerging Markets Finance and Trade, Taylor & Francis Journals, vol. 54(8), pages 1837-1855, June.
    14. Corbet, Shaen & Katsiampa, Paraskevi & Lau, Chi Keung Marco, 2020. "Measuring quantile dependence and testing directional predictability between Bitcoin, altcoins and traditional financial assets," International Review of Financial Analysis, Elsevier, vol. 71(C).
    15. Akhtaruzzaman, Md & Boubaker, Sabri & Lucey, Brian M. & Sensoy, Ahmet, 2021. "Is gold a hedge or a safe-haven asset in the COVID–19 crisis?," Economic Modelling, Elsevier, vol. 102(C).
    16. Urquhart, Andrew & Zhang, Hanxiong, 2019. "Is Bitcoin a hedge or safe haven for currencies? An intraday analysis," International Review of Financial Analysis, Elsevier, vol. 63(C), pages 49-57.
    17. Camilo Mora & Randi L. Rollins & Katie Taladay & Michael B. Kantar & Mason K. Chock & Mio Shimada & Erik C. Franklin, 2018. "Bitcoin emissions alone could push global warming above 2°C," Nature Climate Change, Nature, vol. 8(11), pages 931-933, November.
    18. Jalan, Akanksha & Matkovskyy, Roman & Yarovaya, Larisa, 2021. "“Shiny” crypto assets: A systemic look at gold-backed cryptocurrencies during the COVID-19 pandemic," International Review of Financial Analysis, Elsevier, vol. 78(C).
    19. Bouri, Elie & Molnár, Peter & Azzi, Georges & Roubaud, David & Hagfors, Lars Ivar, 2017. "On the hedge and safe haven properties of Bitcoin: Is it really more than a diversifier?," Finance Research Letters, Elsevier, vol. 20(C), pages 192-198.
    20. Symitsi, Efthymia & Chalvatzis, Konstantinos J., 2018. "Return, volatility and shock spillovers of Bitcoin with energy and technology companies," Economics Letters, Elsevier, vol. 170(C), pages 127-130.
    21. Ratner, Mitchell & Chiu, Chih-Chieh (Jason), 2013. "Hedging stock sector risk with credit default swaps," International Review of Financial Analysis, Elsevier, vol. 30(C), pages 18-25.
    22. Ji, Qiang & Bouri, Elie & Gupta, Rangan & Roubaud, David, 2018. "Network causality structures among Bitcoin and other financial assets: A directed acyclic graph approach," The Quarterly Review of Economics and Finance, Elsevier, vol. 70(C), pages 203-213.
    23. David I. Okorie, 2021. "A network analysis of electricity demand and the cryptocurrency markets," International Journal of Finance & Economics, John Wiley & Sons, Ltd., vol. 26(2), pages 3093-3108, April.
    24. Corbet, Shaen & Lucey, Brian & Yarovaya, Larisa, 2021. "Bitcoin-energy markets interrelationships - New evidence," Resources Policy, Elsevier, vol. 70(C).
    25. Pham, Linh, 2019. "Do all clean energy stocks respond homogeneously to oil price?," Energy Economics, Elsevier, vol. 81(C), pages 355-379.
    26. Wang, Gang-Jin & Ma, Xin-yu & Wu, Hao-yu, 2020. "Are stablecoins truly diversifiers, hedges, or safe havens against traditional cryptocurrencies as their name suggests?," Research in International Business and Finance, Elsevier, vol. 54(C).
    27. Yousaf, Imran & Suleman, Muhammad Tahir & Demirer, Riza, 2022. "Green investments: A luxury good or a financial necessity?," Energy Economics, Elsevier, vol. 105(C).
    28. Wang, Peijin & Zhang, Hongwei & Yang, Cai & Guo, Yaoqi, 2021. "Time and frequency dynamics of connectedness and hedging performance in global stock markets: Bitcoin versus conventional hedges," Research in International Business and Finance, Elsevier, vol. 58(C).
    29. 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.
    30. Elie Bouri & Naji Jalkh & Peter Molnár & David Roubaud, 2017. "Bitcoin for energy commodities before and after the December 2013 crash: diversifier, hedge or safe haven?," Applied Economics, Taylor & Francis Journals, vol. 49(50), pages 5063-5073, October.
    31. Yi, Shuyue & Xu, Zishuang & Wang, Gang-Jin, 2018. "Volatility connectedness in the cryptocurrency market: Is Bitcoin a dominant cryptocurrency?," International Review of Financial Analysis, Elsevier, vol. 60(C), pages 98-114.
    32. Okorie, David Iheke & Lin, Boqiang, 2020. "Crude oil price and cryptocurrencies: Evidence of volatility connectedness and hedging strategy," Energy Economics, Elsevier, vol. 87(C).
    33. Zeng, Ting & Yang, Mengying & Shen, Yifan, 2020. "Fancy Bitcoin and conventional financial assets: Measuring market integration based on connectedness networks," Economic Modelling, Elsevier, vol. 90(C), pages 209-220.
    34. 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.
    35. David Y. Aharon & Zaghum Umar & Xuan Vinh Vo, 2021. "Dynamic spillovers between the term structure of interest rates, bitcoin, and safe-haven currencies," Financial Innovation, Springer;Southwestern University of Finance and Economics, vol. 7(1), pages 1-25, December.
    36. Naeem, Muhammad Abubakr & Karim, Sitara, 2021. "Tail dependence between bitcoin and green financial assets," Economics Letters, Elsevier, vol. 208(C).
    37. Ji, Qiang & Bouri, Elie & Roubaud, David & Kristoufek, Ladislav, 2019. "Information interdependence among energy, cryptocurrency and major commodity markets," Energy Economics, Elsevier, vol. 81(C), pages 1042-1055.
    38. Wang, Pengfei & Zhang, Wei & Li, Xiao & Shen, Dehua, 2019. "Is cryptocurrency a hedge or a safe haven for international indices? A comprehensive and dynamic perspective," Finance Research Letters, Elsevier, vol. 31(C), pages 1-18.
    39. Ji, Qiang & Bouri, Elie & Lau, Chi Keung Marco & Roubaud, David, 2019. "Dynamic connectedness and integration in cryptocurrency markets," International Review of Financial Analysis, Elsevier, vol. 63(C), pages 257-272.
    40. Peng, Xiaofan, 2020. "Do precious metals act as hedges or safe havens for China's financial markets?," Finance Research Letters, Elsevier, vol. 37(C).
    Full references (including those not matched with items on IDEAS)

    Citations

    Citations are extracted by the CitEc Project, subscribe to its RSS feed for this item.
    as


    Cited by:

    1. Júlio Lobão, 2022. "Herding Behavior in the Market for Green Cryptocurrencies: Evidence from CSSD and CSAD Approaches," Sustainability, MDPI, vol. 14(19), pages 1-17, October.
    2. Rui Dias & Nuno Teixeira & Paulo Alexandre & Mariana Chambino, 2023. "Exploring the Connection between Clean and Dirty Energy: Implications for the Transition to a Carbon-Resilient Economy," Energies, MDPI, vol. 16(13), pages 1-21, June.
    3. Duan, Kun & Zhao, Yanqi & Urquhart, Andrew & Huang, Yingying, 2023. "Do clean and dirty cryptocurrencies connect with financial assets differently? The role of economic policy uncertainty," Energy Economics, Elsevier, vol. 127(PA).
    4. Pan Jiang & Hanwen Zhang & Mengyue Li & Yuhan Zhang & Xiujuan Gong & Dong He & Liang Liu, 2023. "Research on the Structural Optimization of the Clean Energy Industry in the Context of Dual Carbon Strategy—A Case Study of Sichuan Province, China," Sustainability, MDPI, vol. 15(4), pages 1-21, February.
    5. Anatolyy Dzyuba & Irina Solovyeva & Dmitry Konopelko, 2023. "Managing Electricity Costs in Industrial Mining and Cryptocurrency Data Centers," International Journal of Energy Economics and Policy, Econjournals, vol. 13(4), pages 76-90, July.
    6. Arfaoui, Nadia & Naeem, Muhammad Abubakr & Boubaker, Sabri & Mirza, Nawazish & Karim, Sitara, 2023. "Interdependence of clean energy and green markets with cryptocurrencies," Energy Economics, Elsevier, vol. 120(C).
    7. Rui Dias & Paulo Alexandre & Nuno Teixeira & Mariana Chambino, 2023. "Clean Energy Stocks: Resilient Safe Havens in the Volatility of Dirty Cryptocurrencies," Energies, MDPI, vol. 16(13), pages 1-24, July.
    8. Chen, Yu & Lin, Boqiang, 2022. "Quantifying the extreme spillovers on worldwide ESG leaders' equity," International Review of Financial Analysis, Elsevier, vol. 84(C).
    9. Pham, Linh & Karim, Sitara & Naeem, Muhammad Abubakr & Long, Cheng, 2022. "A tale of two tails among carbon prices, green and non-green cryptocurrencies," International Review of Financial Analysis, Elsevier, vol. 82(C).
    10. Zhao, Yuan & Liu, Nan & Li, Wanpeng, 2022. "Industry herding in crypto assets," International Review of Financial Analysis, Elsevier, vol. 84(C).
    11. Le, Thanh Ha, 2023. "Quantile time-frequency connectedness between cryptocurrency volatility and renewable energy volatility during the COVID-19 pandemic and Ukraine-Russia conflicts," Renewable Energy, Elsevier, vol. 202(C), pages 613-625.
    12. Walid Mensi & Mariya Gubareva & Hee-Un Ko & Xuan Vinh Vo & Sang Hoon Kang, 2023. "Tail spillover effects between cryptocurrencies and uncertainty in the gold, oil, and stock markets," Financial Innovation, Springer;Southwestern University of Finance and Economics, vol. 9(1), pages 1-27, December.
    13. Siddique, Md Abubakar & Nobanee, Haitham & Karim, Sitara & Naz, Farah, 2023. "Do green financial markets offset the risk of cryptocurrencies and carbon markets?," International Review of Economics & Finance, Elsevier, vol. 86(C), pages 822-833.
    14. Będowska-Sójka, Barbara & Kliber, Agata, 2022. "Can cryptocurrencies hedge oil price fluctuations? A pandemic perspective," Energy Economics, Elsevier, vol. 115(C).
    15. Imran Yousaf & Vasilios Plakandaras & Elie Bouri & Rangan Gupta, 2022. "Hedge and Safe Haven Properties of Gold, US Treasury, Bitcoin, and Dollar/CHF against the FAANA Companies and S&P 500," Working Papers 202227, University of Pretoria, Department of Economics.
    16. Yousaf, Imran & Plakandaras, Vasilios & Bouri, Elie & Gupta, Rangan, 2023. "Hedge and safe-haven properties of FAANA against gold, US Treasury, bitcoin, and US Dollar/CHF during the pandemic period," The North American Journal of Economics and Finance, Elsevier, vol. 64(C).
    17. Lei, Heng & Xue, Minggao & Liu, Huiling & Ye, Jing, 2023. "Precious metal as a safe haven for global ESG stocks: Portfolio implications for socially responsible investing," Resources Policy, Elsevier, vol. 80(C).
    18. Ndubuisi, Gideon & Urom, Christian, 2023. "Dependence and risk spillovers among clean cryptocurrencies prices and media environmental attention," Research in International Business and Finance, Elsevier, vol. 65(C).
    19. Ren, Boru & Lucey, Brian, 2022. "Do clean and dirty cryptocurrency markets herd differently?," Finance Research Letters, Elsevier, vol. 47(PB).
    20. Abakah, Emmanuel Joel Aikins & Wali Ullah, GM & Adekoya, Oluwasegun B. & Osei Bonsu, Christiana & Abdullah, Mohammad, 2023. "Blockchain market and eco-friendly financial assets: Dynamic price correlation, connectedness and spillovers with portfolio implications," International Review of Economics & Finance, Elsevier, vol. 87(C), pages 218-243.
    21. Naeem, Muhammad Abubakr & Gul, Raazia & Farid, Saqib & Karim, Sitara & Lucey, Brian M., 2023. "Assessing linkages between alternative energy markets and cryptocurrencies," Journal of Economic Behavior & Organization, Elsevier, vol. 211(C), pages 513-529.
    22. Ciner, Cetin & Lucey, Brian & Yarovaya, Larisa, 2022. "Determinants of cryptocurrency returns: A LASSO quantile regression approach," Finance Research Letters, Elsevier, vol. 49(C).
    23. Agnese, Pablo & Rios, Francisco, 2023. "Spillover Effects of Energy Transition Metals in Chile," IZA Discussion Papers 15999, Institute of Labor Economics (IZA).

    Most related items

    These are the items that most often cite the same works as this one and are cited by the same works as this one.
    1. Sharif, Arshian & Brahim, Mariem & Dogan, Eyup & Tzeremes, Panayiotis, 2023. "Analysis of the spillover effects between green economy, clean and dirty cryptocurrencies," Energy Economics, Elsevier, vol. 120(C).
    2. Rui Dias & Paulo Alexandre & Nuno Teixeira & Mariana Chambino, 2023. "Clean Energy Stocks: Resilient Safe Havens in the Volatility of Dirty Cryptocurrencies," Energies, MDPI, vol. 16(13), pages 1-24, July.
    3. Waqas Hanif & Hee-Un Ko & Linh Pham & Sang Hoon Kang, 2023. "Dynamic connectedness and network in the high moments of cryptocurrency, stock, and commodity markets," Financial Innovation, Springer;Southwestern University of Finance and Economics, vol. 9(1), pages 1-40, December.
    4. Ahmed, Walid M.A., 2021. "Stock market reactions to upside and downside volatility of Bitcoin: A quantile analysis," The North American Journal of Economics and Finance, Elsevier, vol. 57(C).
    5. Kamal, Javed Bin & Hassan, M. Kabir, 2022. "Asymmetric connectedness between cryptocurrency environment attention index and green assets," The Journal of Economic Asymmetries, Elsevier, vol. 25(C).
    6. Duan, Kun & Zhao, Yanqi & Urquhart, Andrew & Huang, Yingying, 2023. "Do clean and dirty cryptocurrencies connect with financial assets differently? The role of economic policy uncertainty," Energy Economics, Elsevier, vol. 127(PA).
    7. Li, Xingyi & Gan, Kai & Zhou, Qi, 2023. "Dynamic volatility connectedness among cryptocurrencies and China's financial assets in standard times and during the COVID-19 pandemic," Finance Research Letters, Elsevier, vol. 51(C).
    8. Huang, Yingying & Duan, Kun & Urquhart, Andrew, 2023. "Time-varying dependence between Bitcoin and green financial assets: A comparison between pre- and post-COVID-19 periods," Journal of International Financial Markets, Institutions and Money, Elsevier, vol. 82(C).
    9. Rizvi, Syed Kumail Abbas & Naqvi, Bushra & Mirza, Nawazish & Umar, Muhammad, 2022. "Safe haven properties of green, Islamic, and crypto assets and investor's proclivity towards treasury and gold," Energy Economics, Elsevier, vol. 115(C).
    10. Yousaf, Imran & Nekhili, Ramzi & Umar, Muhammad, 2022. "Extreme connectedness between renewable energy tokens and fossil fuel markets," Energy Economics, Elsevier, vol. 114(C).
    11. Al-Shboul, Mohammad & Assaf, Ata & Mokni, Khaled, 2022. "When bitcoin lost its position: Cryptocurrency uncertainty and the dynamic spillover among cryptocurrencies before and during the COVID-19 pandemic," International Review of Financial Analysis, Elsevier, vol. 83(C).
    12. Pham, Linh & Karim, Sitara & Naeem, Muhammad Abubakr & Long, Cheng, 2022. "A tale of two tails among carbon prices, green and non-green cryptocurrencies," International Review of Financial Analysis, Elsevier, vol. 82(C).
    13. Abubakr Naeem, Muhammad & Iqbal, Najaf & Lucey, Brian M. & Karim, Sitara, 2022. "Good versus bad information transmission in the cryptocurrency market: Evidence from high-frequency data," Journal of International Financial Markets, Institutions and Money, Elsevier, vol. 81(C).
    14. Huynh, Toan Luu Duc & Hille, Erik & Nasir, Muhammad Ali, 2020. "Diversification in the age of the 4th industrial revolution: The role of artificial intelligence, green bonds and cryptocurrencies," Technological Forecasting and Social Change, Elsevier, vol. 159(C).
    15. Pham, Son Duy & Nguyen, Thao Thac Thanh & Do, Hung Xuan, 2022. "Dynamic volatility connectedness between thermal coal futures and major cryptocurrencies: Evidence from China," Energy Economics, Elsevier, vol. 112(C).
    16. Mokni, Khaled & Youssef, Manel & Ajmi, Ahdi Noomen, 2022. "COVID-19 pandemic and economic policy uncertainty: The first test on the hedging and safe haven properties of cryptocurrencies," Research in International Business and Finance, Elsevier, vol. 60(C).
    17. Achraf Ghorbel & Wajdi Frikha & Yasmine Snene Manzli, 2022. "Testing for asymmetric non-linear short- and long-run relationships between crypto-currencies and stock markets," Eurasian Economic Review, Springer;Eurasia Business and Economics Society, vol. 12(3), pages 387-425, September.
    18. Ahmed, Walid M.A., 2021. "How do Islamic equity markets respond to good and bad volatility of cryptocurrencies? The case of Bitcoin," Pacific-Basin Finance Journal, Elsevier, vol. 70(C).
    19. Będowska-Sójka, Barbara & Kliber, Agata, 2022. "Can cryptocurrencies hedge oil price fluctuations? A pandemic perspective," Energy Economics, Elsevier, vol. 115(C).
    20. Mensi, Walid & Sensoy, Ahmet & Aslan, Aylin & Kang, Sang Hoon, 2019. "High-frequency asymmetric volatility connectedness between Bitcoin and major precious metals markets," The North American Journal of Economics and Finance, Elsevier, vol. 50(C).

    More about this item

    Keywords

    Cryptocurrencies; Clean energy; Safe haven; Spillovers; Connectedness; DCC-GARCH;
    All these keywords.

    JEL classification:

    • Q4 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Energy
    • G10 - Financial Economics - - General Financial Markets - - - General (includes Measurement and Data)
    • G11 - Financial Economics - - General Financial Markets - - - Portfolio Choice; Investment Decisions
    • G15 - Financial Economics - - General Financial Markets - - - International Financial Markets

    Statistics

    Access and download statistics

    Corrections

    All material on this site has been provided by the respective publishers and authors. You can help correct errors and omissions. When requesting a correction, please mention this item's handle: RePEc:eee:eneeco:v:109:y:2022:i:c:s0140988322001281. See general information about how to correct material in RePEc.

    If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

    If CitEc recognized a bibliographic reference but did not link an item in RePEc to it, you can help with this form .

    If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your RePEc Author Service profile, as there may be some citations waiting for confirmation.

    For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: Catherine Liu (email available below). General contact details of provider: http://www.elsevier.com/locate/eneco .

    Please note that corrections may take a couple of weeks to filter through the various RePEc services.

    IDEAS is a RePEc service. RePEc uses bibliographic data supplied by the respective publishers.