American International Group early this week announced an agreement to sell its mortgage insurance subsidiary, United Guaranty Corp., to Arch Capital Group for $3.4 billion in cash and securities as part of AIG’s plan to become a leaner, more profitable insurer. As of the midway point in 2016, UG was the top private MI in traditional new insurance written, with an 18.8 percent share of the market. Arch MI ranked as the smallest of the seven active firms, with an ...