I would think that if they are willing to arb every cent during the day, they would throw out some bids and offers around the closing prices on the ECNs after 4pm. But they don't. Alot of times i don't get out at 4pm and would like to close out some posiitons after 4pm. But there is just no liquidity within 20 cents. Often i would like to trade at 4:01 if i miss the close, you would think the specialist or someone could throw out some bids/offers around the closing print for late stragglers to close out against. But no luck. And how come no one wants to make a market in XOM premkt or ah's considering thats a 400 billion company. But they don't. Alot of ADRs that trade overseas have some sort of ARB program making a market from early premkt in NYSE. Example, BHP, MT, TS, RTP, BP ect. All of these have an active market with bid/ask very deep premkt. I assume that someone is arbing the local exchange price? Surprising that XOM doesn't have more of a 24hr mkt. I would think that an early riser over in Asia might have an interest in trading XOM in our ah's ect. Or maybe XOM is listed over seas and they just trade it there?