BOSTON—Liberty Mutual Group reported an 8.1% decline in net income for 2009, which fell to $1.02 billion.

Revenue increased 7.8% to $31.09 billion last year. The Boston-based insurer also posted an 11% increase in net premiums written for the year, rising to $28.26 billion. It reported a 99.9% combined ratio for last year compared with 100.1% the previous year.

For the quarter, Liberty Mutual reported a 2% increase in net income of $456 million. Revenues declined 2.6% to $7.94 billion.

Net premiums written for the quarter increased 11.5%, to $7.12 billion. It reported a 99.3% combined ratio vs. 95.3% for the comparable period a year ago.

In a statement, Chairman, President and CEO Edmund F. Kelly said, “Our fourth-quarter and full-year results reflect continued strength of our core businesses in challenging economic and competitive environments. We will uphold our commitment to disciplined underwriting and reserving in order to maintain balance sheet strength.”