With elevated stock/bond correlation of late, it's always worth noting when things move in the opposite direction.  Today was such a day, with stocks making solid gains while bonds managed to hold their ground near unchanged levels.  Corporate bond issuance and stronger economic data also added to ostensible challenges for rates, thus making the ground-holding all the more interesting.  

But here are the caveats:

1. Not every part of the bond market held its ground.  Shorter maturity bonds (like 2yr Treasuries) lost ground.  This pushed the yield curve to its narrowest levels since 2007.  This is a reflection of the positive economic data having clear implications for the Fed's rate hike path (which would affect 2yr yields) but fewer implications for longer-term growth and inflation (which would affect 10yr yields).

2. We could still be seeing temporary distortions surrounding retirement account funding ahead of today's tax deadline.  In other words, money managers have been buying more bonds than they typically would given the other variables in play.

The implicit risk here is that when the curve trading corrects (something it periodically does on its way lower) and when the temporary distortions are behind us, longer-term bonds (and mortgage rates) could be looking at a bit more pressure than they're currently prepared for.