OMAHA, Neb. -- Berkshire Hathaway's fourth-quarter profit more than quadrupled as it received a US$29 billion boost from the new tax law that easily offset any weakness in the company's businesses.

Berkshire said Saturday it earned US$32.6 billion, or US$13.19 per Class B share, in the fourth quarter because of the tax law changes. That compares with US$6.3 billion, or US$2.55 per B share, a year ago.

Most of Berkshire's 90-odd businesses reported improving profits in the quarter, but the company's key insurance units, which include Geico and several major reinsurance companies, reported a US$491 million loss on policy underwriting. That compares with US$548 million gain the previous year.

Berkshire CEO Warren Buffett said he expects the company's insurers will have to pay about $3 billion in claims related to the hurricanes that struck Texas, Florida and Puerto Rico last fall. Those storms are a significant part of why Berkshire's insurance underwriting recorded a loss in 2017 after 14-straight years of underwriting profits.

Berkshire's other businesses, which include BNSF railroad, a number of electric utilities and an assortment of manufacturing and retail businesses, helped offset the insurance losses.

Buffett says investors should pay more attention to operating earnings, which exclude the tax changes and investment values, to get a better sense of how Berkshire's 90-odd businesses are performing. By that measure, Berkshire reported US$3.3 billion operating income, or US$2.23 per B share.

The five analysts surveyed by FactSet expected Berkshire to report operating earnings per Class B share of US$1.76.

Berkshire said its revenue grew nearly 1 per cent in the quarter to US$58.9 billion, up from US$58.3 billion a year ago.

For the full year, Berkshire reported US$44.9 billion net income, or US$18.22 per Class B share. That was nearly double the previous year's US$24.1 billion, or US$9.76 per B share, because of the effects of the tax law.

Berkshire's revenue grew 8 per cent to US$242.1 billion for 2017.

Berkshire also owns clothing, furniture and jewelry firms. And it holds major investments in such companies as Coca-Cola Co., Apple and Wells Fargo & Co.