Changes in the estimated value of some of Berkshire Hathaway Inc.'s investments pushed its second-quarter net income down, but the Omaha company benefited from a lack of natural disasters and gains by its operating businesses.

Berkshire said Friday that it had net income of $3.11 billion, or $1,882 per share, in the second quarter of this year, down 9 percent from $3.42 billion, or $2,072 per share, in the same period last year. Analysts had expected net income of $1,785 per share.

Revenue for the three-month period that ended June 30 was $38.55 billion, up slightly from $38.27 billion in the second quarter of 2011.

The decline in net income came from a $1.07 billion paper loss in the value of Berkshire's derivative investments, a series of insurance-like transactions started several years ago by Warren Buffett, chairman and CEO.

The value of the derivatives fluctuates quarter to quarter. Buffett has said he expects them to be profitable over the long haul, since they expire in an average of 8.