Off-exchange trading: less transparent?

Dark pools are more costly trading venues, according to a survey by the CFA Institute, a global association of investment professionals. Rhodri Preece, director of capital markets policy at the CFA, explains to Jeremy Grant how, in so-called "lit" venues transparency leads to lower buy-sell spreads and offers more stability. He also argues that off-exchange trading should be regulated if it grows into a market rather than bilateral trade.