Go to the web site of the Federal Reserve Bank of St. Louis (FRED) (fred.stlouisfed.org) and for the period from January 1997 to the present, download to the same graph the data series for the BofA Merrill Lynch US Corporate AAA Effective Yield (BAMLC0A1CAAAEY) and the BofA Merrill Lynch US High Yield CCC or Below Effective Yield (BAMLH0A3HYCEY). Describe how the difference between the yields on highgrade corporate bonds and on junk bonds have changed over this period.