Why would the PRIME RATE of grow over time?

the fed dropped the prime rate 1/2 point to 7.75 today. It has seen temporary peaks as high as 21 percent in 1980. It was as low as 4 percent in 2003. However, in 1947 it was 1.75 percent and through the 50′s was 2-3 percent. Overall, the direction has been up. Why would we [...] http://bit.ly/rqD6OH