I am a student lookint at time and sales data for S&P500 and Nasdaq-100 e-mini and regular contracts. The E-minis appear to lead the regulars by about 15 seconds. But I know that the ticks in the time and sales of the regular contracts are entered manually by a floor clerk and there is probably some time delay between the moment when the price changes and when it is recorded. So it's not clear if the E-minis' lead is real or it is simply a result of this reporting time delay. Anybody has an idea of what this time delay might be? I would guess it should not usually exceed 5 seconds but I don't have any evidence to support this guess.