Increasingly throughout the years markets behavior has been dictated by actions of US .
Following actions and words of officials have been important elements in forecasting overall market behavior and direction.
if I understand correctly, before 2008 year the Fund Rate always tried to follow the market trend. After that, rate has been zeroed, and markets start to follow a growing monetary base. And from that moment it is interesting to see chart of S&P and FED BASE overlayed on one another (because they are correlating very well).
But today base is not expanding, at least officially, and rates are still zeroed.
So, FED tries to control effective fund rate via revers REPOs which volume tends to decrease (thus decreasing the real rate)