EXCHANGE STRUCTURE SERIES · No. 1 · 25 FEB TO 24 AUG 2026

The Lit Half Is No Longer Half

Six months of US equities market share in one read: off-exchange crossed 50 percent of consolidated share volume in July and held there, every major lit exchange lost share, and the only exchange of size that grew is the one with a speed bump.

Sapinover Research · August 25, 2026 · 125 sessions of Cboe's published market share data, stitched, deduped and re-verified. First in a series on lit-exchange structure.

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01The Majority Flipped

The off-exchange share of consolidated volume, everything matched away from the lit books and reported through the three FINRA trade reporting facilities, has been moving toward half the tape for years. Over this window it arrived. The first full week above 50 percent was the week of June 1. July averaged above the line, five of the seven full weeks since the start of July have closed above it, and the strongest full week in the window, July 20, printed 51.3 percent.

Monthly averages of daily share. August is partial, through the 24th. Venue counts in parentheses; the renamed Texas venues are carried continuously under their new names.

Three and a half points of consolidated share moved off-exchange in six months. For scale, that is roughly the entire matched share of Cboe BZX, the seventh-largest lit venue, changing sides in half a year. The migration did not come out of one exchange group. NYSE's five venues gave up 1.9 points as a group, Nasdaq's three about 0.4, Cboe's four about 0.8, and the six independent exchanges 0.3.

02Inside the Lit Half

Rank the seventeen continuously operating lit venues by their share change from March to August and the picture is close to monotone decline. Fourteen lost share. Two gained meaningfully. One of those two is a renamed incumbent riding a new brand.

The two names worth sitting with are at opposite ends of the chart.

NYSE Arca lost the most. Down 1.02 points from a 10.7 percent March average, with most of the decline arriving after mid-June. Arca is the ETF exchange: it lists the large majority of US ETFs and its book is where ETF liquidity in the continuous session concentrates. A decline of this size in the venue most exposed to ETF flow, over a window in which off-exchange share rose 3.5 points, is consistent with ETF executions migrating off-exchange, and that hypothesis is testable: the ETF tape and its off-exchange share are exactly what our overnight and internalization work measures. We take that up in a dedicated report.

IEX is the only exchange of size that grew. From 3.74 to 4.28 percent, a 14.5 percent relative gain, and the weekly series is close to a straight line up. Whatever one thinks of the speed bump argument, the market share argument is now empirical: in a six-month window where the lit pool shrank by three and a half points, the venue built around discouraging latency-sensitive strategies took share continuously.

03The New Entrants

The Texas Stock Exchange began live trading on July 10, the first fully integrated new national securities exchange approved in decades. Six weeks in, the tape says this:

A clean launch curve: near zero through the phased rollout, a climb to 0.113 percent in the week of August 3, then an easing to roughly 0.08 percent as launch attention settled. For calibration, 0.08 percent is about twice 24X and eight times LTSE, and about a fifth of the two Texas-branded incumbents.

Which is the sharper observation. Nasdaq BX and NYSE Chicago both renamed themselves Texas venues ahead of the TXSE launch, keeping their CIKs and their MICs. Comparing the 28 sessions before July 10 with the sessions since, NYSE Texas's share rose from 0.387 to 0.437 percent, a 13 percent relative gain, and its March-to-August gain is 30 percent. Nasdaq Texas is roughly flat. On the tape so far, the Texas brand has done more for the incumbent that adopted it than the new exchange that created it.

24X National Exchange, the other newly approved venue, fell from 0.161 to 0.041 percent of consolidated volume across the window, a 75 percent decline. Its significance remains regulatory rather than commercial: its conditional exemptive relief is the backstop mechanism behind the December 6 extended-hours SIP go-live we track weekly in SITREP.

04Where This Series Goes

This report is deliberately a surface read: one public dataset, six months, the moves large enough to see from orbit. Each of the findings above opens a question that share-of-volume data cannot answer, and those are the deep dives this series will take up one at a time.

• The order-type map. Eighteen lit venues, each with its own order type architecture, from IEX's D-Limit to Nasdaq's midpoint extended-life orders to MIAX Pearl's liquidity-code taxonomy. We have already catalogued the fee-schedule architectures in Five Ways US Exchanges Encode Execution Economics. The order-type counterpart, including which types exist at exactly one venue and what that exclusivity is for, is the next reference piece.
• Where Arca's point went. ETF executions by venue class, joining this data with the internalization and overnight ETF work.
• The MEMX question. What a member-owned exchange losing a quarter of its share says about the economics of exchange membership in 2026.
• The auction cut. Cboe's public table reports consolidated share only. Separating continuous from auction volume changes the lit picture materially, and requires venue-level data we will source directly.

First in a series on lit-exchange structure. This analysis is for information only and is not investment advice, a recommendation, or a solicitation. For methodology see the support page.