At yahoo finance, the S&P 500 closed at 1497.74. At stockcharts.com, the S&P 500 closed at 1497.74. But looking at an IB account, they show the 500 at 1498.75, with the ES at 1513.75! With about $13.00 premium for tomorrow, shouldn't ES have closed about 1510.74? Today, as I watched an IB account and the "Arbitrage Meter," I saw people paying a premium in a down trend. Why? I am not claiming that IB's quotes are accurate. If you watch them, you'll see SPX updates less frequently than ES. Why?