Berkshire Hathaway posted a stronger insurance result in the third quarter, but overall company earnings dropped after writedowns on its investment in UK retailer Tesco.

Net profit fell 9% to $US4.62 billion ($5.31 billion) in the three months to September 30, while operating earnings increased 29% to $US4.72 billion ($5.42 billion).

Insurance premiums grew to $US12.72 billion ($14.62 billion) from $US9.27 billion ($10.65 billion), while Berkshire Hathaway Reinsurance Group and General Re results helped lift underwriting earnings to $US629 million ($723 million) from $US170 million ($195 million).

Berkshire Hathaway Reinsurance Group pre-tax profit increased to $US443 million ($509 million) from a loss of $US206 million ($237 million) in the corresponding period last year.

The division benefitted from an absence of major catastrophes, favourable foreign exchange moves and premiums earned on a retroactive agreement with Liberty Mutual.

“We have constrained the volume of this business in recent years due to rates that are, in our view, inadequate,” the company said. “However, we have the capacity and desire to write substantially more business when appropriate pricing can be obtained.”

General Re profit grew to $US126 million ($145 million) from $US63 million ($72 million) as property and casualty gains more than offset a decline in life and health.

Volume increased in selected lines in the division’s North American and international operations, despite strong property and casualty price competition.

Earnings at the Geico car insurance business dropped 14% to $US264 million ($303 million) in the quarter.

Berkshire Hathaway’s insurance investment income fell to $US811 million ($932 million) from $US861 million ($989 million).

For the first nine months of the year, overall company net profit increased to $US15.72 billion ($18.06 billion) from $US14.49 billion ($16.65 billion).