While the headline mortgage applications index made the headlines - rising 18.6% WoW - as mortgage-rates continued to plummet lower, it was the action under the hood that was even more notable.

As mortgage-rates have collapsed to their lowest since Jan 2018, mortgage apps have soared (led by refis).

Note that the rate shift tends to lead applications by around 3-4 weeks, suggesting there is more to come on this mini refi-boom.

In fact purchase mortgage applications growth slowed in the last week, rising just 3.4%; as refinancings exploded 38.5% WoW - the biggest weekly jump since Feb 2015

Perhaps the most ominous sign of all of this is the explosion in Adjustable-rate Mortgages - the second biggest surge since January 2001...