"Get used to it," is what American Capital Agency (AGNC) CIO Gary Kain hears from many about the significant discount to book value his stock (and the entire agency mREIT sector) sell for. If things like banks and closed end funds can trade at discounts, why not agency REITs? It's all about collateral, responds Kain. The fixed agency MBS market is the world's 2nd most liquid, totally transparent, and offers negligible bid/ask spreads.