Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Why don't SPY, SPX, and the e-mini s&p 500 track perfectly with each other?
As a futures trader, I can tell you that the highs and lows for the ES futures diverge simply because they trade around the clock, from 6PM ET to 5PM ET the next day. The SPX is only open during market hours, as is the SPY, but the SPY also trades in the extended hours sessions for about 3.5 hours before and after the regular hours of 930 AM ET to 4PM ET ET. So bottom line, while they pretty much track each other, the difference in their trading hours results in the highs and lows being different.