Warren Buffett has described last year's performance for his Berkshire Hathaway group as "subpar", despite a 45% rise in profits over the period.
In his eagerly anticipated annual letter to investors, Buffett warned in 2013 the growth in Berkshire's book value per share may underperform the S&P 500 when measured over a five-year period for the first time.
"To date, we have never had a five-year period of underperformance, having managed 43 times to surpass the S&P over such a stretch," he wrote.
"But the S&P has now had gains in each of the last four years, outpacing us over that period. If the market continues to advance in 2013, our streak of five-year wins will end."
Buffett said he expects growth in Berkshire's "intrinsic business value" will beat the S&P's returns by small margins over time: "We are confident of that because we have some outstanding businesses, a cadre of terrific operating mangers and a shareholder-oriented culture.
"Our relative performance, however, is almost certain to be better when the market is down or flat. In years when the market is particularly strong, expect us to fall short."
The Sage of Omaha said 2012 was only the ninth year out of the past 48 years he failed to beat the S&P 500 index, as Berkshire's percentage increase in book value was less than the S&P's percentage gain (including dividends and price appreciation).
However, the group still reported a strong rise in profits to $14.8bn (£9.84bn) last year, up from $10.3bn the previous year.
The majority of returns came from paper rises on investments and derivative contracts.
Buffett also said he had reloaded his "elephant gun" and was looking for more acquisition targets.
He said: "We still have plenty of cash and are generating more at a good clip. So it's back to work; Charlie [Munger, the company's vice chairman] and I have again donned our safari outfits and resumed our search for elephants."
Berkshire Hathaway's latest major investment was $12bn in Heinz.