{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,14]],"date-time":"2026-08-14T16:31:25Z","timestamp":1786725085055,"version":"build-2736575974"},"posted":{"date-parts":[[2026]]},"group-title":"SSRN","reference-count":25,"publisher":"Elsevier BV","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:p>Order sizes on Blue Ocean ATS, the dominant overnight trading venue for US National Market System stocks, exhibit pronounced clustering at round-number anchors. Across 273.9 million add events on 30 stocks between August 2025 and March 2026, 40.0 percent of orders sit at exactly one of 34 round-number share counts. The single most common size is 20 shares (5.27 percent of all adds), with secondary peaks at 1 share (4.67 percent), 100 shares (2.84 percent), and 200 shares (2.83 percent). The 20-share mode is anomalous relative to the round-lot conventions documented for NYSE and NASDAQ in prior work (Alexander and Peterson 2007), where modes occur at 500, 1000, and 5000 shares. Hartigan dip tests reject unimodality at the 5 percent level for 30 of 31 tickers; Gaussian mixture model selection by BIC prefers nine or ten components with means clustered at round-number share counts and several components fitting essentially as point masses at exact integers. Cross-ticker round-number clustering ranges from 15 percent (TQQQ) to 67 percent (DIA), and the size of the modal anchor scales with ticker price level. The findings extend the size-clustering literature to a new venue with structurally distinct characteristics-singlevenue continuous overnight market dominated by sponsored-access retail flow-and document a sub-100-share modal anchor that has no counterpart in the published literature on US regularhours equity venues.<\/jats:p>","DOI":"10.2139\/ssrn.6651000","type":"posted-content","created":{"date-parts":[[2026,4,26]],"date-time":"2026-04-26T06:37:31Z","timestamp":1777185451000},"source":"Crossref","is-referenced-by-count":0,"title":["Round-Number Anchoring in Overnight US Equity Order Sizes: Evidence from 274 Million Order Events on the Blue Ocean ATS"],"prefix":"10.2139","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-8477-9393","authenticated-orcid":true,"given":"Boon Chuan","family":"Lim","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"78","reference":[{"issue":"2","key":"ref1","doi-asserted-by":"crossref","first-page":"435","DOI":"10.1016\/j.jfineco.2006.02.005","article-title":"An analysis of trade-size clustering and its relation to stealth trading","volume":"84","author":"G J Alexander","year":"2007","journal-title":"Journal of Financial Economics"},{"issue":"5","key":"ref2","doi-asserted-by":"crossref","first-page":"432","DOI":"10.1002\/fut.20429","article-title":"Size clustering in the FTSE100 index futures market","volume":"30","author":"O Ap Gwilym","year":"2010","journal-title":"Journal of Futures Markets"},{"issue":"2","key":"ref3","doi-asserted-by":"crossref","first-page":"289","DOI":"10.1111\/j.1540-6288.2007.00172.x","article-title":"Price clustering on the Tokyo Stock Exchange","volume":"42","author":"A A?\ufffd?o?lu","year":"2007","journal-title":"The Financial Review"},{"issue":"1","key":"ref4","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1002\/fut.3990050105","article-title":"The degree of price resolution: The case of the gold market","volume":"5","author":"C A Ball","year":"1985","journal-title":"Journal of Futures Markets"},{"issue":"3","key":"ref5","doi-asserted-by":"crossref","first-page":"281","DOI":"10.1016\/0304-405X(93)90029-B","article-title":"Stealth trading and volatility: Which trades move prices","volume":"34","author":"M J Barclay","year":"1993","journal-title":"Journal of Financial Economics"},{"issue":"3","key":"ref6","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1016\/0304-405X(94)90036-1","article-title":"Bid-ask spreads in the interbank foreign exchange markets","volume":"35","author":"H Bessembinder","year":"1994","journal-title":"Journal of Financial Economics"},{"issue":"2","key":"ref7","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1111\/j.1475-6803.2012.01313.x","article-title":"Trade size and price clustering: The case of short sales and the suspension of price tests","volume":"35","author":"B M Blau","year":"2012","journal-title":"Journal of Financial Research"},{"issue":"5","key":"ref8","doi-asserted-by":"crossref","first-page":"2249","DOI":"10.1111\/jofi.13033","article-title":"Tracking retail investor activity","volume":"76","author":"E Boehmer","year":"2021","journal-title":"Journal of Finance"},{"issue":"5","key":"ref9","doi-asserted-by":"crossref","first-page":"453","DOI":"10.1016\/j.pacfin.2006.05.001","article-title":"Which trades move prices in emerging markets? 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