The nation's largest private mortgage insurer, MGIC Investment Corporation (MTG) today reported a net loss for 4Q 2010 of $186.7 million, compared to a net loss of $280.1 million for the same quarter a year ago. Diluted net loss per share was $0.93 for the quarter, compared to diluted loss per share of $2.25 for the same quarter a year ago. New mortgage insurance written in the fourth quarter was $4.2 billion, compared to $3 billion in the fourth quarter of 2009. In addition, the Home Affordable Refinance Program (HARP) accounted for $1.1 billion of insurance that is not included in new insurance written total for the quarter. HARP refinances are treated as a mortgage modifications and therefore count as existing insurance, not new policies. MGIC's net loss for 2010 was $363.7 million, compared to a net loss of $1.32 billion in 2009. For the full year 2010, diluted loss per share was $2.06 compared to a diluted loss per share of $10.65 for the full year 2009. Total revenues for the fourth quarter were $361.1 million, compared to $405.5 million in the fourth quarter last year. Net premiums written for the fourth quarter were $271.4 million, compared to $286.9million for the same period last year. New insurance written for the full year 2010 was $12.3 billion compared to $19.9 billion in 2009. HARP activity for 2010 totaled an additional $3.2 billion. Write to Jacob Gaffney. Follow him on Twitter @JacobGaffney.