'Only $36 billion came from Berkshire's operations, ' he wrote.
The "Oracle of Omaha's" famed annual letter to Berkshire shareholders has become a favourite in the investor calendar but it has attracted heightened interest this year amid rumours that the 87-year-old would unveil plans to step down.
"A large portion of our gain did not come from anything we accomplished at Berkshire", Buffett assured shareholders. "The remaining $29bn was delivered to us in December when Congress rewrote the USA tax code".
Berkshire Hathaway, the conglomerate of which Buffett is CEO and chairman of the board, reported a $65.3 billion gain in net worth in 2017, bolstered largely by the sweeping tax code rewrite pushed through Congress at the end of the year.
The billionaire and CEO of Berkshire Hathaway highlighted a $29 billion tax gain for his company, bemoaned a lack of good deals and reminded his readers that owning stocks through low-priced index funds was the best way to build wealth over time.
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/.
"You and I are lucky to have Ajit and Greg working for us", Buffett told shareholders.
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"Prices for decent, but far from spectacular, businesses hit an all-time high", he said.
Buffett predicted the company's stock will fall again by similar large declines in the next 53 years.
It's important to remember that even Buffett's Berkshire Hathaway (BRK-A, BRK-B) hasn't been immune to significant swings in its stock price either.
The lower tax rate also contributed to a 23% full-year boost in Berkshire's book value, which measures assets minus liabilities and which Buffett considers a good indicator of Berkshire's net worth, to $211,750 per class A share.
Buffett gave the final details of a 10-year long bet he made against hedge funds in 2007.
Edward Jones analyst Jim Shanahan says he expected Buffett to devote more of the letter to explaining his decision to promote and name the top two candidates to eventually succeed him as Berkshire's CEO.
Known to fans as "the Oracle of Omaha", Buffett, 87, has suggested USA stocks are probably the best bet over time, encouraging people to make easy choices and stick with them, eschewing high-fee fund managers, for instance. When the wager concluded on December 31, the index fund had won easily.