Similarly, IBM - of which Berkshire held about 70 million shares on June 30 - is down about 11 percent since the end of the second quarter, with much of that decline occurring after it ditched its 2015 operating earnings target this week. Since June 30, IBM's slump may has cost Berkshire nearly $1.3 billion on paper.
Short-seller Doug Kass has repeatedly pointed to both of those companies as weak spots in Berkshire's portfolio.
Kass, who runs Seabreeze Partners Management in Palm Beach, Florida, was named Buffett's "credentialed bear" for the 2013 Berkshire Hathaway shareholders' meeting. To spice up proceedings at the gathering, which is attended by thousands of Berkshire shareholders, Buffett got Kass to present the bear case against the conglomerate, which owns dozens of businesses selling everything from ice cream to insurance.
"Very few people have the sort of pain threshold and long-term time frame and risk appetite that Warren Buffett has," Kass said. "His risk profile is different than a mere mortal."
Accounting Scandal
Among the other stocks that were in Berkshire's portfolio at June 30 that have dropped significantly are banking group Wells Fargo, credit card group American Express, energy giant Exxon Mobil, Canadian oil producer Suncor Energy and automaker General Motors.
Exxon often sees its fate tied to the price of oil. With crude down about 18 percent so far this year, Buffett's 41 million shares of Exxon at June 30 would be worth almost $311 million less now.
Earlier this month, Berkshire Hathaway said that it had sold off some of its stake in troubled British grocer Tesco, taking it to below 3 percent from around 3.96 percent of Tesco's shares in May.
Those shares are off 45 percent this year in the wake of its worsening performance, exacerbated by an accounting scandal. Buffett himself called that investment a "huge mistake."
Because Berkshire Hathaway owns stock in dozens of companies, several of its holdings are performing better. Retail behemoth Wal-Mart, for example, is up 1.3 percent since the end of the second quarter. And consumer products maker Procter & Gamble is up 7.2 percent from June 30 to Oct. 22.