MBS investments by most of the nation’s publicly traded mortgage real estate investment trusts continue to be in a holding pattern these days as they figure out what to do in an environment of declining interest rates and accelerating prepayment speeds. Market leader Annaly Capital Management held $64.9 billion of agency MBS at midyear, down ever so slightly from the prior quarter. Compared to June 2015, Annaly’s MBS portfolio was off 4.1 percent. American Capital Agency Corp., Annaly’s closest competitor in terms of REIT MBS investing, saw...