Subject: study on execution prices by popular brokerages
A trading experiment uses five retail brokers in 2022, namely, E*Trade (acquired by Morgan Stanley), Fidelity, IBKR, Robinhood, and TD Ameritrade (acquired by Schwab). https://onlinelibrary.wiley.co...

The broker sample covers 87% of the retail brokers who report DAT numbers. TD Ameritrade has by far the most active retail investor base. Across these five brokers, total trading volume is large, averaging around 14 million trades per day. It assumed a typical stock retail trade size of $8,000.

About 53% of total trading volume was on public exchanges and 9% on ATSs, and another 38% was executed by off-exchange market-makers.

The prevailing best quote, defined as the NBBO.It does not include many of the best prices available on exchanges, such as odd lots25 and nondisplayed orders. Indeed, a significant amount of activity transacts within the NBBO (even on exchanges). Fidelity, for example, reports that it generally executes trades at effective spreads that are around 25% of dollar quoted spreads. Fidelity receives very little for payment for order flow; Ameritrade's (Schwab bought) had a lot.

The average round-trip cost ranged from 0.07% to 0.46% for the same trades at different brokerages.

TD Ameritrade was best, followed by Fidelity.