http://finance.yahoo.com/q/bc?s=JNK&t=2y&l=on&z=...
...notice that the 20 year treasury is more volatile than junk bonds.
More apt comparison would be intermediate treasuries, much different picture (time frame also questionable for a pure comparison):
http://etfdb.com/etf/JNK/fundamentals/ http://etfdb.com/etf/IEF/fundamentals/
http://finance.yahoo.com/q/bc?s=JNK&t=2y&l=on&z=...
...notice that the 20 year treasury is more volatile than junk bonds.