If you buy or sell, you are making a forecast yourself. You are predicting that China will open higher or lower (respectively) than the current ask or bid. The market price is discovered through the buying and selling pressures of many market participants. The only way you can make money is by having a better forecast than everyone else. There is no arbitrage opportunity, it's a purely speculative trade.Quote from Tarl_Cabot:
So, if you buy or sell the ETF at any significant amount different from the open, you are accepting other people's forecast - which won't include any event that happens after the US market close.
Basically you're saying that today's closing prices from China are the best possible forecast of tomorrow's open in China; that no possible information available to US market participants could change that. Implicit in this logic is the assumption that NYSE traders don't know jack shit about China.So, it still seems to me to be a good buy if the foreign ETF is less than the open, or a good sell if it is more than the open...