We can appreciate that the daunting task of determining what "the" actual mortgage rate may be at any given moment.  The word "the" is singled out in the previous sentence because there isn't one, perfect, singular, "going rate" for a mortgage.  There's a bell curve with most lenders near the center and a few outliers at the margins.   The only thing that comes close to being a constant across multiple lenders would be the bond market.  Specifically, prices of mortgage-backed securities (MBS) determine the value associated with loans originated by mortgage lenders.  Still, there are numerous variables that lenders control that determine what rates they can offer for any given price level of MBS. Looking at an individual rate quote from an individual lender is one way to know something fairly specific about rates, but of course things can still change for a variety of reasons between the initial quote and the closing table. In order to get a general idea of where mortgage rates are, it's common to turn to a rate index.  In terms of circulation and historical availability, Freddie Mac's weekly rate index is the only game in town.  Unfortunately, in terms of accuracy, on shorter time horizons, it leaves something to be desired--especially for those interested in knowing day to day changes.  Freddie's survey is a 5 day average collected from Thursday through Wednesday and then reported the following day.  When things are moving quickly, that means several inputs to the equation will no longer be relevant.  We've also noticed that Freddie can quite simply undershoot the reality of a big, directional move, like the one we've seen take shape over the past 5 days. There's no telling why this occurs, but it could have something to do with the fact that--even after methodology changes--Freddie's survey still involves human input of rates that aren't necessarily available anymore.