Seminar Recap: Market Structure and Trading Trends with Nasdaq’s Phil Mackintosh

Last month, Tower had the pleasure of hosting Phil Mackintosh, Chief Economist and Senior Vice President at Nasdaq, for an insightful seminar on U.S. equities and options market structure. Phil walked us through how market dynamics have evolved in recent years –  highlighting both key structural shifts and trading trends that continue to change across U.S. markets today.

Shifts in Equity Volumes

Equity trading volumes have surged since the pandemic, fueled by events such as the meme-stock craze, geopolitical shocks like the Russia–Ukraine conflict, and U.S. election cycles. These periods of heightened activity have reinforced the importance of liquidity providers. Phil emphasized the role of arbitrage and market making in ensuring orderly markets, where the ability to connect fragmented liquidity across venues is critical to both efficiency and price discovery.

The Rise of Options Trading

Options markets have experienced similar growth, driven in part by the proliferation of contracts and shorter-dated expiries, including the now-popular 0DTE options. While this expansion provides traders with more flexibility, it also creates new challenges. The industry now needs infrastructure that can handle heavier message traffic, the ability to price a broader universe of symbols, and support faster-paced risk management.

Retail and Institutional Order Flow

Phil also addressed how order flow segmentation is reshaping U.S. equity markets. Retail trades, often routed through wholesalers, follow very different pathways than institutional flow, which often interact with  alternative trading systems (ATSs) and exchanges, as well as new bi-lateral trading relationships. Off-exchange activity has been increasing, with bi-lateral trading and retail wholesalers playing a more prominent role. Understanding these distinct channels is essential to appreciating how liquidity is formed, how different participants achieve best execution, and how market quality is measured across venues.

Evolving Market Structure

There was also discussion on 24-hour trading, a rapidly growing trend and topic in equities. While enabling round-the-clock access and supporting more global participation in U.S. Markets, Phil emphasized significant practical challenges. Ranging from corporate action processing and timing, settlement process and trading hours alignment. In the near future, understanding these opportunities while weighing the resulting operational complexity and key infrastructure changes will be key. It seems clear the debate will continue as technology and demand evolve.

Phil’s seminar was a reminder of how dynamic U.S. market structure is and how every adjustment in rules, products, or technology can have cascading effects across equities and options markets. For us, it was both a valuable learning opportunity and a chance to reflect on how these trends intersect with our own trading strategies and market participation.