Over the years, Buffett has lavished equal praise on both, but provided little indication as to his preferences about who he thinks will succeed him.
President Donald Trump's tax overhaul, which lowered corportate tax rates to 21% from 35%, pumped up the company's profits by $29.1 billion.
Berkshire has United States dollars 116 billion in cash and government bonds that Buffett wants to deploy to increase the earnings of its non-insurance businesses.More news: Korean 'Iron Man' Kim wins historic Olympic skeleton gold
Buffett is the third-richest person in the world, with a net worth of $86.3 billion, according to the Bloomberg Billionaires Index.
Said Buffett in Saturday's annual letter: "You and I are lucky to have Ajit and Greg working for us. The remaining $29bn was delivered to us in December when Congress rewrote the USA tax code". He said that high purchase prices were a barrier for "virtually all" the deals the billionaire investor looked at in 2017.
Here's what to watch for in the latest letter from Buffett, 87, which is set for release online Saturday at 8 a.m.at Berkshire's home page http://www.berkshirehathaway.com/. "Only $36 billion came from Berkshire's operations".
Buffett says the asking prices for potential acquisitions reached an all-time high in 2017.More news: Arrested After 14-Month-Long Probe Into Russian Embassy Cocaine Smuggling
"If Wall Street analysts or board members urge that brand of CEO to consider possible acquisitions, it's a bit like telling your ripening teenager to be sure to have a normal sex life", he wrote. And it holds major investments in such companies as Coca-Cola Co., Apple and Wells Fargo & Co.
Operating profit fell 18 per cent to $14.5bn due to a $2.2bn loss from the group's insurance underwriting unit as a string of natural disasters hit the US.
Its net earnings rose from $24.07 billion in 2016 to $44.94 billion as of December 31. Berkshire's "A" shares also became the first stock ever to reach a price of $300,000. It's a number that sticks out like a sore thumb compared to gains from previous years.
Warren Buffett said in his annual letter the practice of managing portfolio risk using a specified ratio of bonds-to-stocks is flawed.More news: PSL-3: Glitzy opening ceremony underway at Dubai International Cricket Stadium
Buffett touted his win in a bet that he made 10 years ago, in which he basically wagered that a low-priced index fund tracking the S&P 500 stock index would post better returns over the next decade than a portfolio of five fund of funds run by high-fee hedge fund managers, often considered the "smart money" on Wall Street.