Fannie Mae has selected National Mortgage Insurance Corp. to insure a pool of approximately $5.0 billion of mortgages as the GSE looks to expand its risk sharing with private firms, the mortgage insurer announced this week.The Emeryville, CA-based unit of NMI Holdings explained that the transaction was offered through a formal bid process to private mortgage insurers.“Fannie Mae selected National MI as the insurer based on its favorable terms and conditions, and beneficial risk-share attributes,” said National MI.