The average daily trading volume in agency MBS fell to $189.4 billion in March, the lowest reading of the year, and a sign that liquidity may still be an issue, depending on which seat you’re in. According to figures compiled by the Securities Industry and Financial Markets Association, the trading numbers for 2016, so far, haven’t exactly lit the world on fire. In January and February, the readings were $195.1 billion and $201.4 billion, respectively. Last year, the best reading was...