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This study uses minute-by-minute data for the SPY ETF from 2008 to 2014 to test intraday volume dynamics. Results show a U-shaped volume pattern, the lowest activity between 12:45 and 13:00, and differences by weekday and daily price dynamics. Findings can support optimal timing for large orders and high-frequency trading while minimizing ETF price impact.",{"@graph":63,"@context":119},[64,80,102],{"@type":65,"itemListElement":66},"BreadcrumbList",[67,71,74,77],{"item":68,"name":69,"@type":70,"position":9},"https://docshare.wps.com","Home","ListItem",{"item":72,"name":10,"@type":70,"position":73},"https://docshare.wps.com/template/",2,{"item":75,"name":11,"@type":70,"position":76},"https://docshare.wps.com/template/presentations/",3,{"item":78,"name":59,"@type":70,"position":79},"https://docshare.wps.com/template/intraday-patterns-in-the-trading-volume-of-the-spy-etf/563263/",4,{"url":78,"name":59,"@type":81,"image":82,"author":87,"headline":59,"publisher":90,"fileFormat":93,"inLanguage":57,"description":61,"dateModified":94,"datePublished":95,"encodingFormat":93,"isAccessibleForFree":96,"interactionStatistic":97},"DigitalDocument",{"url":83,"@type":84,"width":85,"height":86},"https://docshare.wps.com/thumbnails/intraday-patterns-in-the-trading-volume-of-the-spy-etf/563263.png","ImageObject",442,249,{"name":88,"@type":89},"vwvw","Person",{"url":68,"name":91,"@type":92},"DocShare","Organization","application/pdf","2026-10-25","2026-10-12",true,{"@type":98,"interactionType":99,"userInteractionCount":101},"InteractionCounter",{"@type":100},"ViewAction",7,{"@type":103,"mainEntity":104},"FAQPage",[105,111,115],{"name":106,"@type":107,"acceptedAnswer":108},"Why do trading volumes tend to be high at market open and close?","Question",{"text":109,"@type":110},"High volumes at open are explained by information-based trading, while high volumes near close are linked to portfolio rebalancing needs.","Answer",{"name":112,"@type":107,"acceptedAnswer":113},"What is the key intraday volume pattern found for the SPY ETF?",{"text":114,"@type":110},"The intraday trading volume variation is U-shaped, with the lowest trading activity occurring between 12:45 and 13:00.",{"name":116,"@type":107,"acceptedAnswer":117},"Which factors affect intraday volume patterns in the study?",{"text":118,"@type":110},"The patterns vary by weekday and by the overall daily price dynamics.","https://schema.org",{"og:url":78,"og:type":121,"og:title":59,"og:site_name":91,"og:description":61},"article",{"robots":123,"canonical":78},"index,follow",{"doc_id":125,"site_id":56},563263,1792247995,{"code":4,"msg":5,"data":128},{"doc_id":125,"user_id":129,"nickname":88,"user_avatar":130,"doc_module":9,"category_id":8,"category_name":11,"doc_title":59,"doc_description":61,"doc_content":131,"file_id":132,"file_url":133,"file_type":134,"file_size":135,"view_count":101,"is_deleted":4,"is_public":9,"is_downloadable":9,"audit_status":9,"page_count":136,"language":137,"language_code":57,"site_id":56,"html_lang":57,"table_of_contents":138,"faqs":139,"seo_title":140,"seo_description":61,"update_tm":141,"read_time":79},3985747874149,"https://ap-avatar.wpscdn.com/avatar/3a001161165b4dc3d9e?x-image-process=image/resize,m_fixed,w_180,h_180&k=1790129441039064114","Intraday Patterns in the Trading Volume of the SPY ETF  \nEmiliano Giudici, PhD.  \nDepartment of Economics and Finance  \nStephen F. Austin State University  \nPO Box 13009, SFA Station  \nNacogdoches  \nHaiying Hu, MPA  \nSchool of Accounting  \nStephen F. Austin State University  \nJiao Tong University, Shanghai  \nChina  \nAbstract  \nLiterature indicates that trading volumes of stocks and ETFs tends to be high at open and at market close. Explanations for this pattern include information based trading (leading to high trading volumes at open) and portfolio rebalancing (leading to high volumes at the end of the day). Using different models, we examine the minute-by-minute trading volumes of the SPY ETF from 2008 to 2014. We find that a) the variation of trading volume through the trading day is U-shaped; b) we identified 12:45 to13:00 as the time of day with the lowest trading activity; c) the patterns of intraday trading volumes vary by weekday and by the overall daily price dynamics. Our findings could help high frequency traders and large investors who are seeking optimal trading times to place large orders while minimizing their impact on ETF prices.  \nKeyword: ETFs, Trading Volume, Market Microstructure, Financial Instruments, Intraday Returns  \nJEL codes: G120, G190, G230  \n1.Introduction  \nWith the increased availability of transaction level data, many studies have examined how volume, returns and risk change through the trading day. At a first glance, many studies show that the trading volume of assets tends to be high at market open, it decreases until about noon and it picks up gradually until market close, resembling the shape of a“U”. Knowing the presence of predictable patterns in the trading volumes of securities is important to investors who aim to successfully find a counterpart to a buy or sell order.  \nThe U-shaped pattern of intraday trading volume has been documented across financial instruments, trading venues and time periods. In the U.S. equity markets, Blau (2009) finds U-shaped volumes in NYSE traded stocks, Wang and Wang (2016) find it in the SPDR ETF. Abhyankar (1997) finds U-shaped volumes in the London Stock Exchange, Lee (2001) finds it in the Taiwanese Stock Exchange and Hussain (2011) finds it in the DAX 30. High volumes at open and close are also found in derivatives markets: Peterson (1990) finds them in the CBOE and Eaves (2010) finds this pattern in the Tokyo futures exchange. Furthermore, while the general patterns of intraday volumes are consistent, Kimatz (2003) show that there are differences in volume by day of the week – with peaks on Tuesdays and minimum volumes on Monday and Fridays.  \nThe variation in intraday volumes has been explained in terms of interactions between informed and liquidity traders. Liquidity traders need to trade to meet liquidity needs, which are random in nature, while informed traders will trade only in response to information. To the extent that information clusters during non-trading hours, it could explain the high volume at market open. On the other end, the need to rebalance portfolios (in mutual funds or ETFs) could be responsible for increasing the trading volume around market close.  \nStudies in intraday volatility patterns have less consensus: Agarwall (2013) and Eaves (2010) find a reversed J-shape intraday volatility in Indian and Japanese futures, respectively. Diao (2015) does not find such pattern in the CSI300 . Finally, studies on intraday returns do not illustrate a clear pattern, indicating that intraday returns have dynamics that are even more complex than volume or volatility.  \nOverall, while the literature on intraday trading volumes seems to focus on the general shape of the intraday trading volumes, we did not find any study that identifies the time when the trading volume is at its lowest.  \nKnowledge and predictability of the intraday trading volumes could be beneficial to a) day traders, who may not be able to execute a strategy in a timely f","cbCaiaFM5kPUepac","https://ap.wps.com/l/cbCaiaFM5kPUepac","pdf",583992,10,"English","# 1. Introduction\n# 2. Data and Methodology\n## 2a. Data","[{\"question\":\"Why do trading volumes tend to be high at market open and close?\",\"answer\":\"High volumes at open are explained by information-based trading, while high volumes near close are linked to portfolio rebalancing needs.\"},{\"question\":\"What is the key intraday volume pattern found for the SPY ETF?\",\"answer\":\"The intraday trading volume variation is U-shaped, with the lowest trading activity occurring between 12:45 and 13:00.\"},{\"question\":\"Which factors affect intraday volume patterns in the study?\",\"answer\":\"The patterns vary by weekday and by the overall daily price dynamics.\"}]","Intraday Patterns in the Trading Volume of the SPY ETF | PDF",1791825087]