“Dark pools of liquidity” have recently become the focus of increased regulatory scrutiny, including a number of high-profile enforcement actions related to these alternative trading systems. This increased scrutiny follows on the heels of Michael Lewis’s popular book, “Flash Boys,” which introduced the public at large to dark pools through its allegations that high frequency trading firms use dark pools to game the system to the detriment of common investors. But what exactly are dark pools and do they have any redeeming qualities? This post provides a primer on the benefits and disadvantages of dark pools and why they matter.
In general, “dark pools of liquidity” are private alternative forums for trading securities that are typically used by large institutional investors and operate outside of traditional “lit” exchanges like NASDAQ and the NYSE. The key characteristic of dark pools is that, unlike “lit” exchanges, the identity and amount of individual trades are not revealed. The pools typically do not publicly display quotes or provide prices at which orders will be executed. Dark pools, and trading in dark pools, have proliferated in recent years due in part to the fragmentation of financial trading venues coupled with advancements in technology, including online trading. There are currently over 40 dark pools operating in the United States. Around half of these are owned by large broker-dealers and are operated for the benefit of their clients and for their own proprietary traders. According to the SEC, the percentage of total trading volume executed in dark venues has increased from approximately 25% in 2009 to approximately 35% today.