SPY does not track SP 500 index?

Can someone explain why the spy is down 0.28% today to 147.67 but the SP 500 index is down 0.71 to 1470.58.

It seems the spy is traded between 4 to 4:15, and the close at 4:15 is used as its closing price. I'm not too sure so appreciate if someone can clarify.

 

I thought it tracked SP Futures?

SPX tracks cash, SPY tracks futures. I could be wrong.

 

SPY is an ETF designed to track the SPX cash however due to normal trading fluctuations and fees incurred by the ETF, as well as the fact it is rounded off sinec it is 1/10th the SPX, leads to slight differences between SPY and SPX.

 

None of those index ETF's correlate 100%. But they are all above 95%. I recall that QQQQ does the best job. The cynic in me thinks the difference is the vig the boyz get for giving you the opportunity to play against them.

 

And don't forget that SPY pays a dividend that needs to be calculated into the difference.

 

Exactly

 

SPY ETF is also listed on Onechicago as a Future. So The dividend is taken out of the contract.

 

No. Look up the standard future pricing model and you will see why.

 

Single Stock Futures = Stock price * (1+ interest rate/ 360 * days to expiry) - dividends owed to Expiry