S&P 500 vs 10 Year Treasury Yield

The Dow is up 200 points today, yet bond yields are barely budging.  This continues the divergence that has been occurring in the bond market since operation twist in September.  Below is a chart of the S&P and the 10 year yield over the last five years.  Although the two were reasonably correlated since 07, bond yields have remained flat as stocks have rallied since last fall.