The chart above shows the S&P 500 in the upper inset and the HYG:TLT ratio in the lower inset. Note that with the market's recent attempts to make new highs, the HYG:TLT line has not confirmed this move, instead continuing to head south.
Such a non-confirmation or divergence has proven to be something worth keeping in mind. Bearish divergences in 2007, 2010 and 2011 were quite timely as the HYG:TLT ratio did not confirm the trend in the S&P 500. Also, the bullish divergence in late 2008 / early 2009 suggested that the stock market's vicious decline was coming to an end, with the HYG:TLT bottoming in December 2008 and making a higher low in March 2009.