Interest rates slightly up? And, the future has a delta higher than 1... because of the interest. So if projected dividends stay the same in dollar terms, the future outperforms the spot slightly when we move up. Together with maybe a small rise in rate...
A rise in rate of 10 bp is about 0.20 in the 1-month future, 2.5 points in 1-year.
And the move from 2450 to 2550 means a 1-year future goes up by an extra 1.25 points compared to spot, assuming 1.25%. (Basically, the 1-year future has a delta of 1.0125)