Essent Group Ltd. (NYSE: ESNT), NMI Holdings Inc. (Nasdaq: NMIH) and Radian Group Inc. (NYSE: RDN) may all be forced to slash their premiums after rival MGIC Investment Corp. (NYSE: MTG) announced premium cuts. Shares of Essent Group plummeted $6.46 to close at $35.61, NMI Holdings plunged $4.00 to close at $13.70, Radian Group tumbled $3.03 to close at $16.11 and MGIC investment dropped $2.20 to close at $10.62.