Fannie Mae and Freddie Mac could suffer losses of nearly $2 billion on the fair value of their assets if interest rates fluctuate upward by just a single percentage percent, according to the Federal Housing Finance Agency’s official watchdog. A white paper issued this week by the FHFA’s Office of Inspector General found that despite moves by the Finance Agency and the Treasury to require the two government-sponsored enterprises to substantially downsize their mortgage asset portfolios, interest rate risk remains a “significant concern.” “The increasingly illiquid nature of the GSEs’ mortgage asset portfolios presents...