"With over 50 years of experience, we know that a simple so-called index fund … does actually better than professional money managers," said economist Burton Malkiel.
Other venues have been allowing round-the-clock trading for years.
The New York Stock Exchange would allow trades 22 hours a day through its electronic platform, Arca, pending regulatory approval.
A new report on stock trading by members of Congress reveals possible conflicts of interest.
The head of the Securities and Exchange Commission has taken aim at the commission-free business model.
