Remember the "QE-on vs QE-off" trading in 2013?  In an extremely overt way, stocks and bonds rallied and sold together based on constantly evolving prospects for Fed tapering.  It occurred perfectly between the Fed meeting that introduced tapering possibilities and the Fed meeting that confirmed it.

While it hasn't been on the same scale, we do see echoes of this same type of trading from time to time.  These are especially evident when the ECB or Fed are on the near-term calendar or if an official is making a comment that seems to affect ECB/Fed accommodation prospects.

That's exactly what happened overnight tonight when ECB's Couere said they may 'front-load' bond buying ahead of a less liquid summer trading season.  Stocks and bonds both improved on the news, but especially German bonds. 

US markets would have their own "accommodation trade" (or in this case a "contraction trade") as Housing Starts data unequivocally suggested the "weak winter."  The data crushed forecasts--especially in the northeast--and hit the best levels since late 2007. 

All this a day before we get FOMC Minutes and 3 days before Yellen gives a speech on her economic outlook.  The implication is that either the Fed will give a clue or markets will be more likely to interpret what's said as justification for an earlier rate hike.

For what it's worth, the general malaise in Treasuries, specifically, is highly attributable to a much bigger-than-expected slate of corporate bond issuance.