Retail Order

In market microstructure research and regulatory discussions, retail orders occupy a distinct category from institutional or professional orders based on their origin, size, and informational characteristics. A retail order is placed by an individual investor — whether through a traditional brokerage account, a discount online brokerage, or a mobile trading app — and typically involves quantities of a few hundred to a few thousand shares in liquid equities. These orders represent the savings and investment activity of ordinary individuals rather than the capital allocation decisions of hedge funds, pension funds, or professional trading desks.

The defining economic characteristic of retail order flow, from a market microstructure perspective, is its low adverse selection content. Academic research on order flow decomposition consistently finds that retail orders are less likely than institutional orders to be submitted by traders acting on material non-public or superior private information. Retail investors generally buy and sell based on personal financial needs, rebalancing decisions, news reactions, or directional views formed from publicly available information. Because retail orders carry relatively little private information, market makers who trade against them face lower risk of being caught on the wrong side of a large informed trade.

This uninformed nature of retail order flow makes it economically attractive to wholesale market makers. By separating retail order flow from institutional order flow — the latter of which may carry more adverse selection risk — wholesalers can price retail executions more favorably than the anonymous order flow traded on public exchanges. This economic logic underlies the payment for order flow (PFOF) system, in which retail brokerages are compensated for routing their customers' orders to wholesalers rather than to exchanges.

From the retail investor's perspective, the quality of execution on a small individual order is determined primarily by the effective spread — the difference between the execution price and the midpoint of the NBBO at the time of the order. Retail investors placing market orders in liquid large-cap U.S. equities typically receive executions at or very close to the NBBO midpoint, often with explicit price improvement over the quoted best price. For smaller, less liquid stocks, however, spreads widen considerably and the execution quality advantage of the wholesaler model is less consistent.

The SEC requires brokerages to disclose where they route retail orders under Rule 606, and requires the venues executing those orders (including wholesalers) to publish monthly execution quality statistics under Rule 605. These disclosures allow retail investors, consumer advocates, and researchers to assess whether the routing decisions made by brokerages are consistent with best execution requirements. The growth of zero-commission trading at major retail brokerages in 2019 intensified public and regulatory scrutiny of these routing arrangements, prompting the SEC's equity market structure reform proposals of 2022 and 2023.