It was an up and down week for mortgage backed securities last week. Despite better than expected economic data, MBS didn’t give up too much ground and mortgage rates did manage to dip to 4.75%. However by week’s end, rates had risen to 4.875% for the best qualified consumers. To remind readers, mortgage rates are determined by the trading of mortgage backed securities. As the price increases, lenders can generally pass along lower mortgage rates. As prices fall lenders offer higher mortgage rates which returns a greater yield to the end buyer of the MBS....