Raijiv Sethi raises the idea that increased focus on algorithmic trading is removing the support for smaller size capitalisation and reducing the number of public limited companies.
In addition, stock market structure today is geared for large‐capitalization stocks with typically symmetrical order books but disastrous for the vast majority of small‐capitalization stocks with asymmetrical order books (where there is not naturally an offsetting buy order to match against a sell order and vice versa)... The “Flash Crash” was an example of where even normally liquid securities went to a state of “asymmetry” and price discovery broke down...
[Until] all trades, quotes and other messages in all interrelated markets are tagged and traceable to the trading venue, broker and ultimate investor, and disclosed to the market, markets will not be perceived as fair... With full tagging, tracking and reporting and the application of posttrade analysis and test bed techniques such as Agent‐Based Models, regulators and market participants will... once and for all be in a position to judge the impact of other participants and to regulate and plan accordingly...